How do I make my image backgroung transparent?

I have an image without a background that is just checkered. However, when I render it the background is just black.
How do I make it transparent? Please help.

You need to mix the image with a transparent node by the alpha factor. If you are using Blender Internal or Cycles it will be a little different . . .

Thanks, but that only makes the whole image transparent. I’d like to get rid of the black background.

It works like this:


Thanks very much! I forgot to connect the alpha with the factor.