I'm working in the first CS.
I have an 8.5 x 11 box filled with a multi-colored blend (using the gradient tool).
I want to draw a small thin white box over top of it that fades from 100% white to zero (clear).
I cannot figure this one out. I know this is a very easy "do" in Photoshop, but cannot get this to work in Illustrator.
You will need to use an Opacity mask (from the Transparency Palette) with a black to white gradient.