I don't know now, at first I believed him because I thought steroid use by some of the big stars was obvious, but there is a guy on ESPN Page 2 who has done some fact checking on Canseco. Some of the stuff he says happened isn't true. For example, he says he remembers a crucial at-bat during Game 6 of a playoff series (can't remember which one), but there wasn't even a Game 6 during that series.
Here's the link:
http://sports.espn.go.com/espn/page2...=merron/050216