FACTBOX: Rules about steroid use in U.S. sport

(Reuters) - Prosecutors said on Thursday that baseball home run king Barry Bonds tested positive for steroids in November 2000, months before his record-breaking 73-home run season.

The allegation came in a legal filing in Bonds' steroid perjury case. On Wednesday, pitching great Roger Clemens said he never used illegal drugs in testimony to Congress over allegations he received injections of steroids.

Following are the current rules regarding performance-enhancing steroids in various U.S. sports:

MAJOR LEAGUE BASEBALL

* Banned the use of steroids in 1991 but did not start testing for it until 2003 and penalties were light. Amphetamine use is also prohibited.

* A first positive test would result in treatment and a second would lead to a 15-day suspension. Only on the fifth positive test would a player be banned from playing for one year.

* In December 2005, the baseball players' association approved a proposal by team owners to tighten up the steroid policy. Under new rules, a positive test result causes a 50-game ban without pay. A player would be suspended for 100 games for a second positive test and banned for life for the third positive result, although players can seek reinstatement after a two-year suspension. Rules regarding use of amphetamines were also tightened.

NATIONAL FOOTBALL LEAGUE

* Prohibits the use of anabolic steroids, certain stimulants and human or animal growth hormones in addition to agents known to mask the presence of the drugs in urine.