This works, I just need to add the transform() function because
I'm using integer fields. I'll revise my code as such.

However, it would be nice to know if this is "error by design" or
sort of a bug.

I love that: Error by Design.

>Use this instead:
>select * from test where iif(empty(x),.t.,f1$x)
>select * from test where iif(x='none',.t.,f1$x)
>
>>Is this normal VFP (7 or 8) Select-SQL behavior?
>>

>>create cursor test (f1 i)
>>for i = 1 to 10
>>	insert into test values (i)
>>endfor
>>x='1,2,3,4,5'
>>*!*	x=''  && uncomment to cause an error
>>select * from test where iif(empty(x),.t.,f1 in (&x))
>>*!*	x='none'  && uncomment to cause an error
>>select * from test where iif(x='none',.t.,f1 in (&x))
>>