Edges out of focus

[Tadao]

How come when I take a group photo the people on the ends are always out of focus?

Thanks,
Tadao

[Digidave]

Could be many things. Usually a poor quality lens though. If you let us see an example, we could give you better help.

[kencaleno]

What lens are you using?

[kentuckyranger]

It's called barrel distortion.
When using a lens of poor quality the barrel distortion is more pronounced.

It could also be a dirty lens.
If a lens isn't cleaned properly oil from your fingers, dirt and dust can collect at the edge of the lens, throwing its focus off.

I agree with the rest, we need to see a photo and know what kind of camera and lens you're using to really be helpful.