diff --git a/hkmc2/shared/src/main/scala/hkmc2/bbml/bbML.scala b/hkmc2/shared/src/main/scala/hkmc2/bbml/bbML.scala
index 31ca23852..13e823ff9 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/bbml/bbML.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/bbml/bbML.scala
@@ -448,11 +448,11 @@ class BBTyper(using elState: Elaborator.State, tl: TL):
             effBuff += eff
             nestCtx += sym -> rhsTy
             goStats(stats)
-          case TermDefinition(Fun, sym, params, sig, Some(body), _) :: stats =>
-            typeFunDef(sym, params match {
-              case S(params) => Term.Lam(params, body)
-              case _ => body // * may be a case expressions
-            }, sig, ctx)
+          case TermDefinition(Fun, sym, ParamList(_, ps) :: Nil, sig, Some(body), _) :: stats =>
+            typeFunDef(sym, Term.Lam(ps, body), sig, ctx)
+            goStats(stats)
+          case TermDefinition(Fun, sym, Nil, sig, Some(body), _) :: stats =>
+            typeFunDef(sym, body, sig, ctx)  // * may be a case expressions
             goStats(stats)
           case TermDefinition(Fun, sym, _, S(sig), None, _) :: stats =>
             ctx += sym -> typeType(sig)
diff --git a/hkmc2/shared/src/main/scala/hkmc2/codegen/Block.scala b/hkmc2/shared/src/main/scala/hkmc2/codegen/Block.scala
index 94706f7a2..9ee982c8c 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/codegen/Block.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/codegen/Block.scala
@@ -74,7 +74,7 @@ sealed abstract class Defn:
 final case class TermDefn(
     k: syntax.TermDefKind,
     sym: TermSymbol,
-    params: Opt[Ls[Param]],
+    params: Ls[ParamList],
     body: Block,
 ) extends Defn
 
diff --git a/hkmc2/shared/src/main/scala/hkmc2/codegen/js/JSBuilder.scala b/hkmc2/shared/src/main/scala/hkmc2/codegen/js/JSBuilder.scala
index 0fbe435ed..471beeff4 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/codegen/js/JSBuilder.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/codegen/js/JSBuilder.scala
@@ -12,6 +12,8 @@ import hkmc2.semantics.Elaborator
 import hkmc2.syntax.Tree
 import hkmc2.semantics.TopLevelSymbol
 import hkmc2.semantics.MemberSymbol
+import hkmc2.semantics.ParamList
+import hkmc2.codegen.Value.Lam
 
 
 // TODO factor some logic for other codegen backends
@@ -99,11 +101,14 @@ class JSBuilder extends CodeBuilder:
         result(Value.This(sym))
       val (thisProxy, res) = scope.nestRebindThis(defn.sym):
         val defnJS = defn match
-        case TermDefn(syntax.Fun, sym, N, body) =>
+        case TermDefn(syntax.Fun, sym, Nil, body) =>
           TODO("getters")
-        case TermDefn(syntax.Fun, sym, S(ps), bod) =>
-          val vars = ps.map(p => scope.allocateName(p.sym)).mkDocument(", ")
-          doc"function ${sym.nme}($vars) { #{  # ${body(bod)} #}  # }"
+        case TermDefn(syntax.Fun, sym, ParamList(_, ps) :: pss, bod) =>
+          val paramList = ps.map(p => scope.allocateName(p.sym)).mkDocument(", ")
+          val result = pss.foldRight(bod):
+            case (ParamList(_, ps), block) => 
+              Return(Lam(ps, block), false)
+          doc"function ${sym.nme}(${paramList}) { #{  # ${body(result)} #}  # }"
         case ClsDefn(sym, syntax.Cls, mtds, flds, ctor) =>
           val clsDefn = sym.defn.getOrElse(die)
           val clsParams = clsDefn.paramsOpt.getOrElse(Nil)
@@ -118,11 +123,12 @@ class JSBuilder extends CodeBuilder:
           }) { #{  # ${
             ctorCode.stripBreaks
           } #}  # }${
-            mtds.map: td =>
-              val vars = td.params.getOrElse(Nil).map(p => scope.allocateName(p.sym)).mkDocument(", ")
-              doc" # ${td.sym.nme}($vars) { #{  # ${
-                body(td.body)
-              } #}  # }"
+            mtds.map: 
+              case td @ TermDefn(_, _, ParamList(_, ps) :: Nil, _) =>
+                val vars = ps.map(p => scope.allocateName(p.sym)).mkDocument(", ")
+                doc" # ${td.sym.nme}($vars) { #{  # ${
+                  body(td.body)
+                } #}  # }"
             .mkDocument(" ")
           }${
             if mtds.exists(_.sym.nme == "toString")
diff --git a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
index 3238fa835..3dbde1955 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/semantics/Elaborator.scala
@@ -428,12 +428,14 @@ extends Importer:
                 case S(t) => typeParams(t)
                 case N => (N, ctx)
               // Add parameters to context
-              val (ps, newCtx) = td.paramLists.foldLeft((Ls[Param](), newCtx1)):
-                    case ((ps, ctx), t) => params(t)(using ctx).mapFirst(ps ++ _)
-                  .mapFirst(some)
+              val (pss, newCtx) = 
+                td.paramLists.foldLeft(Ls[ParamList](), newCtx1):
+                  case ((pss, ctx), ps) => 
+                    val (qs, newCtx) = params(ps)(using ctx)
+                    (pss :+ ParamList(ParamListFlags.empty, qs), newCtx)
               val b = rhs.map(term(_)(using newCtx))
               val r = FlowSymbol(s"‹result of ${sym}›", nextUid)
-              val tdf = TermDefinition(k, sym, ps,
+              val tdf = TermDefinition(k, sym, pss,
                 td.signature.orElse(newSignatureTrees.get(id.name)).map(term), b, r)
               sym.defn = S(tdf)
               tdf
@@ -592,8 +594,8 @@ extends Importer:
   def computeVariances(s: Statement): Unit =
     val trav = VarianceTraverser()
     def go(s: Statement): Unit = s match
-      case TermDefinition(k, sym, ps, sign, body, r) =>
-        ps.foreach(_.foreach(trav.traverseType(S(false))))
+      case TermDefinition(k, sym, pss, sign, body, r) =>
+        pss.foreach(ps => ps.params.foreach(trav.traverseType(S(false))))
         sign.foreach(trav.traverseType(S(true)))
         body match
           case S(b) =>
diff --git a/hkmc2/shared/src/main/scala/hkmc2/semantics/Term.scala b/hkmc2/shared/src/main/scala/hkmc2/semantics/Term.scala
index 8f9686754..bd5ed716f 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/semantics/Term.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/semantics/Term.scala
@@ -113,7 +113,7 @@ sealed trait Statement extends AutoLocated:
     case Assgn(lhs, rhs) => lhs :: rhs :: Nil
     case Deref(term) => term :: Nil
     case TermDefinition(k, _, ps, sign, body, res) =>
-      ps.toList.flatMap(_.flatMap(_.subTerms)) ::: sign.toList ::: body.toList
+      ps.toList.flatMap(_.subTerms) ::: sign.toList ::: body.toList
     case cls: ClassDef =>
       cls.paramsOpt.toList.flatMap(_.flatMap(_.subTerms)) ::: cls.body.blk :: Nil
     case td: TypeDef =>
@@ -175,7 +175,7 @@ sealed trait Statement extends AutoLocated:
     case Error => "<error>"
     case Tup(fields) => fields.map(_.showDbg).mkString("[", ", ", "]")
     case TermDefinition(k, sym, ps, sign, body, res) => s"${k.str} ${sym}${
-      ps.fold("")(_.map(_.showDbg).mkString("(", ", ", ")"))
+      ps.map(_.showDbg).mkString("")
     }${sign.fold("")(": "+_.showDbg)}${
       body match
         case S(x) => " = " + x.showDbg
@@ -194,7 +194,7 @@ final case class DefineVar(sym: LocalSymbol, rhs: Term) extends Statement
 final case class TermDefinition(
     k: TermDefKind,
     sym: TermSymbol,
-    params: Opt[Ls[Param]],
+    params: Ls[ParamList],
     sign: Opt[Term],
     body: Opt[Term],
     resSym: FlowSymbol,
@@ -272,6 +272,17 @@ final case class Param(flags: FldFlags, sym: LocalSymbol & NamedSymbol, sign: Op
 
 object FldFlags { val empty: FldFlags = FldFlags(false, false, false) }
 
+final case class ParamListFlags(ctx: Bool):
+  def showDbg: Str = (if ctx then "ctx " else "")
+  override def toString: String = "‹" + showDbg + "›"
+
+object ParamListFlags:
+  val empty = ParamListFlags(false)
+
+final case class ParamList(flags: ParamListFlags, params: Ls[Param]):
+  def subTerms: Ls[Term] = params.flatMap(_.subTerms)
+  def showDbg: Str = flags.showDbg + params.mkString("(", ", ", ")")
+
 trait FldImpl extends AutoLocated:
   self: Fld =>
   def children: Ls[Located] = self.value :: self.asc.toList ::: Nil
diff --git a/hkmc2/shared/src/main/scala/hkmc2/typing/TypeChecker.scala b/hkmc2/shared/src/main/scala/hkmc2/typing/TypeChecker.scala
index ddd2d50ce..1b730b0e0 100644
--- a/hkmc2/shared/src/main/scala/hkmc2/typing/TypeChecker.scala
+++ b/hkmc2/shared/src/main/scala/hkmc2/typing/TypeChecker.scala
@@ -30,7 +30,7 @@ class TypeChecker(using raise: Raise):
       ts.defn match
         case S(td: TermDefinition) =>
           td.params match
-            case N => P.Flow(td.resSym)
+            case Nil => P.Flow(td.resSym)
     case Blk(stats, res) =>
       // val p1 = stats.map(typeStat)
       // val p2 = typeProd(res)
@@ -40,7 +40,7 @@ class TypeChecker(using raise: Raise):
       stats.foreach:
         case t: TermDefinition =>
           t.sign.map(typeProd)
-          t.params.map(typeParams)
+          t.params.map(_.params).map(typeParams)
           t.body.map(typeProd)
           P.Ctor(LitSymbol(Tree.UnitLit(true)), Nil)
         case t: Term =>
@@ -57,10 +57,12 @@ class TypeChecker(using raise: Raise):
       ts.defn match
       case S(td: TermDefinition) =>
         td.params match
-          case N =>
+          case Nil =>
             val f = typeProd(r)
             constrain(P.exitIf(f, ts, r.refNum, rc), C.Fun(typeProd(tup), C.Flow(app.resSym)))
-          case S(ps) =>
+          case ParamList(_, ps) :: Nil =>
+            // App applies to the leftmost parameter list
+            // TODO: how to recursively check the subsequent Apps (if any)?
             if ps.size != args.size then
               raise(ErrorReport(
                 msg"Expected ${ps.size.toString} arguments, but got ${
diff --git a/hkmc2/shared/src/test/mlscript/basics/MultiParamLists.mls b/hkmc2/shared/src/test/mlscript/basics/MultiParamLists.mls
index 83b5abc15..989e9297d 100644
--- a/hkmc2/shared/src/test/mlscript/basics/MultiParamLists.mls
+++ b/hkmc2/shared/src/test/mlscript/basics/MultiParamLists.mls
@@ -1,16 +1,64 @@
 :js
+:sjs
 
+fun f(n1: Int): Int = n1
+//│ JS:
+//│ function f(n1) { return n1 }; undefined
 
-// FIXME elbaoration is currently wrong
+f(42)
+//│ JS:
+//│ this.f(42)
+//│ = 42
 
-:sjs
-fun foo(x)(y) = x * y
+fun f(n1: Int)(n2: Int): Int =  (10 * n1 + n2)
 //│ JS:
-//│ function foo(x, y) { return x * y }; undefined
+//│ function f(n1) { return (n2) => { let tmp; tmp = 10 * n1; return tmp + n2 } }; undefined
 
-:sjs
-fun foo(x)(y)(z) = x * y + z
+f(4)(2)
 //│ JS:
-//│ function foo(x, y, z) { let tmp; tmp = x * y; return tmp + z }; undefined
+//│ let tmp; tmp = this.f(4); tmp(2)
+//│ = 42
 
+fun f(n1: Int)(n2: Int)(n3: Int): Int = 10 * (10 * n1 + n2) + n3
+//│ JS:
+//│ function f(n1) {
+//│   return (n2) => {
+//│     return (n3) => {
+//│       let tmp, tmp1, tmp2;
+//│       tmp = 10 * n1;
+//│       tmp1 = tmp + n2;
+//│       tmp2 = 10 * tmp1;
+//│       return tmp2 + n3
+//│     }
+//│   }
+//│ };
+//│ undefined
 
+f(4)(2)(0)
+//│ JS:
+//│ let tmp, tmp1; tmp = this.f(4); tmp1 = tmp(2); tmp1(0)
+//│ = 420
+
+fun f(n1: Int)(n2: Int)(n3: Int)(n4: Int): Int = 10 * (10 * (10 * n1 + n2) + n3) + n4
+//│ JS:
+//│ function f(n1) {
+//│   return (n2) => {
+//│     return (n3) => {
+//│       return (n4) => {
+//│         let tmp, tmp1, tmp2, tmp3, tmp4;
+//│         tmp = 10 * n1;
+//│         tmp1 = tmp + n2;
+//│         tmp2 = 10 * tmp1;
+//│         tmp3 = tmp2 + n3;
+//│         tmp4 = 10 * tmp3;
+//│         return tmp4 + n4
+//│       }
+//│     }
+//│   }
+//│ };
+//│ undefined
+
+f(3)(0)(3)(1)
+//│ JS:
+//│ let tmp, tmp1, tmp2; tmp = this.f(3); tmp1 = tmp(0); tmp2 = tmp1(3); tmp2(1)
+//│ = 3031