Lighting -> shadow trouble

I’ve been pulling my hair out because of this problem.
I have 2 objects, lighted by 1 lamp with no shadow options and a 1 spot with ray shadow, and only shadow.
The second object, behind the first and whose alpha is at the moment 0, is been seen in the shadow of object 1.
For the objects i have tried Ztransp. But then i could see the shadow of both objects when they are alpha 0.
What is the best lighting option when you need shadow and alpha.
I hope i made myself clear…
Thanx, Twan