Transparant picturebackground

Hi…

I want to move a cloud from one side to the other in my Flash movie. Therefore i’d like to have that cloud without a background ( transparant), so I use Photoshop, export it as a gif with transparancy. Everything works well until then, but when I try to import the cloud in Flash it’s always with in a rectangle with a white background, so it doesn’t look good. Who can help me. I heard once that you have to save it as a .tif and than import it, but it just won’t work…Please help