[oddnumber]

I have two pictures and I would like to merge them into one- for a side by side comparison. Is there a way to do this in iphoto?

[mtorbin]

Actually, there's a really unique way that you can do this:
1) Create a new "album" and put those two pictures in that album
2) Increase the zoom level in the "Organize" tab until you have them situated the way you like.
It's not perfect, but it's a quick fix.
- MT

[Duke_Thomas]

If all you want to do is compare the two images side by side, would just displaying them in two separate windows do? I.e., right-click (control-click) the image, "Edit in separate window."

[oddnumber]

Yeah, but I want them to print together on one page.

[OldToad]

Put them both into an album, select the album and click on the Print button. In the Print window select N-Up under style and and 2 under Photos per page. Do not click on the One photo per page box. Of course you will have had to previously selected the appropriate paper size under Page Setup.
Hope this has been of some help. Good luck.