You don't pass properties by reference, you pass the pointer to the form:

DO FORM Foo WITH THISFORM

In your Foo form:

LPARAMETERS oForm
oForm.Prop = "Some value"

HTH

>What is the syntax for passing a form property by reference?
>
>Foo(@THISFORM.prop)
>
>gives me an error. I've tried every combo I can think of (@THISFORM..prop, THISFORM.@prop, @(THISFORM.prop), ...). I give up, please tell me the syntax!!