Its always hard to tell in some cases. Ill list some pre 1990 because I think a lot could be using them like in other sports. Ones that raise suspicion just off the top of my head... Ken Norton Mike Weaver Evander Holyfield Michael Spinks (25 lbs in 3 months? I know Spinks was cutting at 175 but I don't recall a lot of fat on Spinks during this time, also his association with Mackie Shillstone who also helped Holyfield and his weight gain) Late 80s Ray Leonard (puts on a whole bunch of muscle and attributes it to pushups)