Paris - Serena Williams claims she is the victim of "discrimination" by US doping chiefs who are testing her more than other players.
At Wimbledon Williams slammed "shocking" treatment over excessive targeting from testers in the run-up to the second Grand Slam of the season.
And in a tweet on Wednesday the 23-time Grand slam winner reignited the discussion.
".....and it’s that time of the day to get "randomly" drug tested and only test Serena," she posted on her official Twitter page.
"Out of all the players it’s been proven I’m the one getting tested the most. Discrimination? I think so. At least I’ll be keeping the sport clean #StayPositive," she wrote.
The 36-year-old battled back from life-saving surgery after giving birth to get within touching distance of an eighth Wimbledon title.
However, the American suffered a straight sets defeat by Angelique Kerber in the women's final on July 14.
She had arrived at the tournament on the back of a report revealing her anger about an unannounced test in June where the tester refused to leave her Florida house.
Williams said at the time she had been tested five times on June, compared to one or none from some of her compatriots.
Athletes returning from a long absence are often the subject of repeated drug tests, as they are seen as part of a higher-risk category than athletes in the flow of regular competition.
...and it’s that time of the day to get “randomly” drug tested and only test Serena. Out of all the players it’s been proven I’m the one getting tested the most. Discrimination? I think so. At least I’ll be keeping the sport clean #StayPositive— Serena Williams (@serenawilliams) July 25, 2018
But I’m ready to do whatever it takes to have a clean sport so bring it on. I’m excited.— Serena Williams (@serenawilliams) July 25, 2018