Tennis is adopting the biological passport program and increasing the number of blood tests as part of a new anti-doping drive that players themselves have demanded.
Pete Sampras believes tennis is free of performance-enhancing drugs now, as well as during his 14-year pro career that ended in 2002.

The 15-time Grand Slam winner will replace top-ranked Victoria Azarenka in next week's rankings after coming from a set down to beat former Wimbledon champion Petra Kvitova 3-6, 6-3, 7-5 on Friday in the quarterfinals of the Qatar Open.
Serena Williams spent most of the past week downplaying the prospect of returning to the top of the rankings. Then it happened and she couldn't hold back the tears.
The ATP was not doing enough to protect players' health and the increase in hard-court events will lead to long-term injuries that will affect players after they retire, Rafael Nadal said Tuesday.
Rafael Nadal criticized the ATP on Tuesday for not doing enough to protect players' health, saying the increase in hard-court events will lead to long-term injuries that will affect players after they retire.
Rafael Nadal says testing for performance-enhancing drugs in sport should strike a balance between catching the cheats and respecting the athletes.
In years past, Novak Djokovic marked his victories at the Australian Open with rowdy late-night celebrations and bleary-eyed photo shoots the next morning in downtown Melbourne.