diff --git a/Upsilon/BaseTypes/TypeConversion.cs b/Upsilon/BaseTypes/TypeConversion.cs
new file mode 100644
index 0000000..2514d80
--- /dev/null
+++ b/Upsilon/BaseTypes/TypeConversion.cs
@@ -0,0 +1,30 @@
+using System;
+using Upsilon.BaseTypes.Number;
+
+namespace Upsilon.BaseTypes
+{
+    public static class TypeConversion
+    {
+        public static LuaType ToLuaType(this object o)
+        {
+            switch (o)
+            {
+                case bool b:
+                    return new LuaBoolean(b);
+                case int i:
+                    return new NumberLong(i);
+                case long i:
+                    return new NumberLong(i);
+                case float f:
+                    return new NumberDouble(f);
+                case double f:
+                    return new NumberDouble(f);
+
+
+                default:
+                    throw new Exception();
+            }
+
+        }
+    }
+}
\ No newline at end of file
diff --git a/Upsilon/Evaluator/Evaluator.cs b/Upsilon/Evaluator/Evaluator.cs
index c233640..d0a3f7b 100644
--- a/Upsilon/Evaluator/Evaluator.cs
+++ b/Upsilon/Evaluator/Evaluator.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using Upsilon.BaseTypes;
 using Upsilon.BaseTypes.Number;
 using Upsilon.Binder;
@@ -35,15 +36,23 @@ namespace Upsilon.Evaluator
             return _returnValue;
         }
 
-        public LuaType Evaluate(BoundScript e, string functionName)
+        public LuaType Evaluate(BoundScript e, string functionName, ImmutableArray<LuaType> parameters)
         {
             Evaluate(e.Statement);
             if (!Scope.TryGet(functionName, out var statement) || statement.Type != Type.Function)
             {
                 throw new ArgumentException(($"Function '{functionName}' could not be found"));
             }
+            var function = (LuaFunction) statement;
             var innerEvaluator = new Evaluator(_diagnostics, Scope);
-            var result = innerEvaluator.Evaluate(((LuaFunction)statement).Block);
+            for (var index = 0; index < parameters.Length; index++)
+            {
+                var parameter = parameters[index];
+                var parameterName = function.Parameters[index];
+                innerEvaluator.Scope.Set(parameterName, parameter);
+            }
+
+            var result = innerEvaluator.Evaluate(function.Block);
             return result;
         }
 
diff --git a/Upsilon/Evaluator/Script.cs b/Upsilon/Evaluator/Script.cs
index b3b0afb..583b7e8 100644
--- a/Upsilon/Evaluator/Script.cs
+++ b/Upsilon/Evaluator/Script.cs
@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using Upsilon.BaseTypes;
 using Upsilon.Binder;
 using Upsilon.Parser;
@@ -39,9 +40,17 @@ namespace Upsilon.Evaluator
             return Evaluator.Evaluate(Bind());
         }
 
-        public object EvaluateFunction(string functionName)
+        public object EvaluateFunction(string functionName, object[] parameters = null)
         {
-            return Evaluator.Evaluate(Bind(), functionName);
+            var luaParameters = ImmutableArray.CreateBuilder<LuaType>();
+            if (parameters != null)
+            {
+                foreach (var parameter in parameters)
+                {
+                    luaParameters.Add(parameter.ToLuaType());
+                }
+            }
+            return Evaluator.Evaluate(Bind(), functionName, luaParameters.ToImmutable());
         }
 
         public T Evaluate<T>() where T : LuaType
@@ -49,9 +58,17 @@ namespace Upsilon.Evaluator
             return (T)Evaluator.Evaluate(Bind());
         }
 
-        public T EvaluateFunction<T>(string functionName) where T : LuaType
+        public T EvaluateFunction<T>(string functionName, object[] parameters = null) where T : LuaType
         {
-            return (T)Evaluator.Evaluate(Bind(), functionName);
+            var luaParameters = ImmutableArray.CreateBuilder<LuaType>();
+            if (parameters != null)
+            {
+                foreach (var parameter in parameters)
+                {
+                    luaParameters.Add(parameter.ToLuaType());
+                }
+            }
+            return (T)Evaluator.Evaluate(Bind(), functionName, luaParameters.ToImmutable());
         }
 
         public string PrettyPrintSyntaxTree()
diff --git a/UpsilonTests/FunctionTests.cs b/UpsilonTests/FunctionTests.cs
index 55a1bb0..7123178 100644
--- a/UpsilonTests/FunctionTests.cs
+++ b/UpsilonTests/FunctionTests.cs
@@ -166,5 +166,44 @@ end
             Assert.Equal(100, (long)result);
         }
 
+        [Fact]
+        public void ReturnFromCSharpCallWithParameter()
+        {
+            const string input = @"
+function testFunc (b)
+    if b then
+        return 100
+    else
+        return 50
+    end
+end
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var result = script.EvaluateFunction<NumberLong>("testFunc", new object[] {true});
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal(100, (long)result);
+            var result2 = script.EvaluateFunction<NumberLong>("testFunc", new object[] {false});
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal(50, (long)result2);
+
+        }
+
+        [Fact]
+        public void ReturnFromCSharpCallWithParameters()
+        {
+            const string input = @"
+function add (a, b)
+    return a + b
+end
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var result = script.EvaluateFunction<NumberLong>("add", new object[] {400, 128});
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Equal(528, (long)result);
+
+        }
+
     }
 }
\ No newline at end of file