diff --git a/crates/generate/src/funcs.rs b/crates/generate/src/funcs.rs
index 13eff6baa1..e788032e66 100644
--- a/crates/generate/src/funcs.rs
+++ b/crates/generate/src/funcs.rs
@@ -308,6 +308,11 @@ fn marshal_arg(
             }
         }
         witx::Type::Union(_u) => read_conversion,
+        witx::Type::Handle(_h) => {
+            let name = names.func_param(&param.name);
+            let handle_type = names.type_ref(tref, anon_lifetime());
+            quote!( let #name = #handle_type::from(#name); )
+        }
         _ => unimplemented!("argument type marshalling"),
     }
 }
diff --git a/crates/generate/src/types.rs b/crates/generate/src/types.rs
index bd05467d38..05154ded3e 100644
--- a/crates/generate/src/types.rs
+++ b/crates/generate/src/types.rs
@@ -21,7 +21,7 @@ pub fn define_datatype(names: &Names, namedtype: &witx::NamedType) -> TokenStrea
                 }
             }
             witx::Type::Union(u) => define_union(names, &namedtype.name, &u),
-            witx::Type::Handle(_h) => unimplemented!("handle types"),
+            witx::Type::Handle(h) => define_handle(names, &namedtype.name, &h),
             witx::Type::Builtin(b) => define_builtin(names, &namedtype.name, *b),
             witx::Type::Pointer(p) => define_witx_pointer(
                 names,
@@ -398,10 +398,73 @@ fn define_enum(names: &Names, name: &witx::Id, e: &witx::EnumDatatype) -> TokenS
     }
 }
 
+fn define_handle(names: &Names, name: &witx::Id, h: &witx::HandleDatatype) -> TokenStream {
+    let ident = names.type_(name);
+    let size = h.mem_size_align().size as u32;
+    let align = h.mem_size_align().align as u32;
+    quote! {
+        #[derive(Copy, Clone, Debug, ::std::hash::Hash, Eq, PartialEq)]
+        pub struct #ident(u32);
+
+        impl From<#ident> for u32 {
+            fn from(e: #ident) -> u32 {
+                e.0
+            }
+        }
+
+        impl From<#ident> for i32 {
+            fn from(e: #ident) -> i32 {
+                e.0 as i32
+            }
+        }
+
+        impl From<u32> for #ident {
+            fn from(e: u32) -> #ident {
+                #ident(e)
+            }
+        }
+        impl From<i32> for #ident {
+            fn from(e: i32) -> #ident {
+                #ident(e as u32)
+            }
+        }
+
+        impl ::std::fmt::Display for #ident {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                write!(f, "{}({})", stringify!(#ident), self.0)
+            }
+        }
+        impl wiggle_runtime::GuestType for #ident {
+            fn size() -> u32 {
+                #size
+            }
+            fn align() -> u32 {
+                #align
+            }
+            fn name() -> String {
+                stringify!(#ident).to_owned()
+            }
+            fn validate(ptr: &wiggle_runtime::GuestPtr<#ident>) -> Result<(), wiggle_runtime::GuestError> {
+                Ok(())
+            }
+        }
+        impl<'a> wiggle_runtime::GuestTypeClone<'a> for #ident {
+            fn read_from_guest(location: &wiggle_runtime::GuestPtr<'a, #ident>) -> Result<#ident, wiggle_runtime::GuestError> {
+                let r = location.as_ref()?;
+                Ok(*r)
+            }
+            fn write_to_guest(&self, location: &wiggle_runtime::GuestPtrMut<'a, Self>) {
+                unsafe { (location.as_raw() as *mut #ident).write(*self) };
+            }
+        }
+        impl<'a> wiggle_runtime::GuestTypeCopy<'a> for #ident {}
+    }
+}
+
 fn define_builtin(names: &Names, name: &witx::Id, builtin: witx::BuiltinType) -> TokenStream {
     let ident = names.type_(name);
     let built = names.builtin_type(builtin, quote!('a));
-    if let witx::BuiltinType::String = builtin {
+    if builtin.needs_lifetime() {
         quote!(pub type #ident<'a> = #built;)
     } else {
         quote!(pub type #ident = #built;)
diff --git a/tests/atoms.rs b/tests/atoms.rs
index 216613766f..e9be5479b6 100644
--- a/tests/atoms.rs
+++ b/tests/atoms.rs
@@ -14,7 +14,10 @@ impl atoms::Atoms for WasiCtx {
         println!("INT FLOAT ARGS: {} {}", an_int, an_float);
         Ok(())
     }
-    fn double_int_return_float(&mut self, an_int: u32) -> Result<f32, types::Errno> {
+    fn double_int_return_float(
+        &mut self,
+        an_int: u32,
+    ) -> Result<types::AliasToFloat, types::Errno> {
         Ok((an_int as f32) * 2.0)
     }
 }
@@ -75,7 +78,7 @@ impl DoubleIntExercise {
             self.return_loc.ptr as i32,
         );
 
-        let return_val: GuestRef<f32> = guest_memory
+        let return_val: GuestRef<types::AliasToFloat> = guest_memory
             .ptr(self.return_loc.ptr)
             .expect("return loc ptr")
             .as_ref()
diff --git a/tests/atoms.witx b/tests/atoms.witx
index ef496d7600..932d7c9ffd 100644
--- a/tests/atoms.witx
+++ b/tests/atoms.witx
@@ -1,5 +1,7 @@
 (use "errno.witx")
 
+(typename $alias_to_float f32)
+
 (module $atoms
   (@interface func (export "int_float_args")
     (param $an_int u32)
@@ -8,5 +10,5 @@
   (@interface func (export "double_int_return_float")
     (param $an_int u32)
     (result $error $errno)
-    (result $doubled_it f32))
+    (result $doubled_it $alias_to_float))
 )
diff --git a/tests/handles.rs b/tests/handles.rs
new file mode 100644
index 0000000000..ed86a04519
--- /dev/null
+++ b/tests/handles.rs
@@ -0,0 +1,76 @@
+use proptest::prelude::*;
+use wiggle_runtime::{GuestError, GuestType};
+use wiggle_test::{impl_errno, HostMemory, MemArea, WasiCtx};
+
+const FD_VAL: u32 = 123;
+
+wiggle_generate::from_witx!({
+    witx: ["tests/handles.witx"],
+    ctx: WasiCtx,
+});
+
+impl_errno!(types::Errno);
+
+impl handle_examples::HandleExamples for WasiCtx {
+    fn fd_create(&mut self) -> Result<types::Fd, types::Errno> {
+        Ok(types::Fd::from(FD_VAL))
+    }
+    fn fd_consume(&mut self, fd: types::Fd) -> Result<(), types::Errno> {
+        println!("FD_CONSUME {}", fd);
+        if fd == types::Fd::from(FD_VAL) {
+            Ok(())
+        } else {
+            Err(types::Errno::InvalidArg)
+        }
+    }
+}
+
+#[derive(Debug)]
+struct HandleExercise {
+    pub return_loc: MemArea,
+}
+
+impl HandleExercise {
+    pub fn test(&self) {
+        let mut ctx = WasiCtx::new();
+        let mut host_memory = HostMemory::new();
+        let mut guest_memory = host_memory.guest_memory();
+
+        let e = handle_examples::fd_create(&mut ctx, &mut guest_memory, self.return_loc.ptr as i32);
+
+        assert_eq!(e, types::Errno::Ok.into(), "fd_create error");
+
+        let h_got: u32 = *guest_memory
+            .ptr(self.return_loc.ptr)
+            .expect("return ptr")
+            .as_ref()
+            .expect("return ref_mut");
+
+        assert_eq!(h_got, 123, "fd_create return val");
+
+        let e = handle_examples::fd_consume(&mut ctx, &mut guest_memory, h_got as i32);
+
+        assert_eq!(e, types::Errno::Ok.into(), "fd_consume error");
+
+        let e = handle_examples::fd_consume(&mut ctx, &mut guest_memory, h_got as i32 + 1);
+
+        assert_eq!(
+            e,
+            types::Errno::InvalidArg.into(),
+            "fd_consume invalid error"
+        );
+    }
+
+    pub fn strat() -> BoxedStrategy<Self> {
+        (HostMemory::mem_area_strat(types::Fd::size()))
+            .prop_map(|return_loc| HandleExercise { return_loc })
+            .boxed()
+    }
+}
+
+proptest! {
+    #[test]
+    fn handle_exercise(e in HandleExercise::strat()) {
+        e.test()
+    }
+}
diff --git a/tests/handles.witx b/tests/handles.witx
new file mode 100644
index 0000000000..69c1b0546e
--- /dev/null
+++ b/tests/handles.witx
@@ -0,0 +1,12 @@
+(use "errno.witx")
+
+(typename $fd (handle))
+
+(module $handle_examples
+  (@interface func (export "fd_create")
+    (result $error $errno)
+    (result $fd $fd))
+  (@interface func (export "fd_consume")
+    (param $fd $fd)
+    (result $error $errno))
+)