do i need an antivirus for my macbook pro?

Lora ...

Viruses aren't so much the issue as malware.

Great article here > Thomas' Corner : Mac Virus and Malware Guide

Definitely one to avoid is Symantec's Norton. This link includes results from an ASC Symantec / Norton search > Community Search: Apple Support Communities

i think u dont need it, u just need it if ur going to share some archives with a wondows..

ClamXav is widely recommended among many users in here. And, best of all, it's free!