MacOS X Compatibility:
Photoshop 7 and up (including Photoshop CS3 & CS4)
Photoshop Elements 3, 4, or 6
Fully Compatible with Mac OSX through 10.6 (Snow Leopard)
Windows Compatibility:
Photoshop 6 and up (including Photoshop CS3 & CS4)
Photoshop Elements 3, 4, 5 or 6
Fully Vista Compatible