Sophos Anti-Virus is, by far, the best anti-virus product for the Macintosh, and I've used them all. Too bad it isn't sold to end users...they sell only to business/enterprise customers (education, too). They provide definition updates (IDE's) faster than Symantec and NAI (most of the time), and their software can also be used to scan messages for a mail server (with some kind of software passing messages to it). Their support is better than Symantec and NAI, too, IMHO. And unlike Symantec, they don't charge you for definition updates after a year. And unlike NAI's Virex, their software actually works and doesn't cause other problems.