When installing Adobe Premiere Elements 10 for Mac, please follow the updated instructions provided on this support page.
Adobe Premiere Elements supported import/export formats include:
AVCHD, Blu-ray Disc (export only), DV-AVI (import/export on Windows, import only on Mac OS), DVD, Dolby® Digital Stereo, H.264, HDV, MPEG-1 (import only), MPEG-2, MPEG-4, MP3, QuickTime, Windows Media (Windows only), and many more. Import/export of some formats may require activation via an Internet connection. Activation is fast, easy, and free.