Six-time Olympic sprint champion Usain Bolt insists he is "clean" in the wake of failed drugs tests by fellow Jamaican athletes.
Asafa Powell and Sherone Simpson recently tested positive, as did American Tyson Gay, the fastest man in the world this year.
Bolt, who races at the London Anniversary Games, said: "I'm clean.
"But you have to be very careful as an athlete because right now there are a lot of things on the banned list."
The Jamaican added: "You have to keep up to date with this kind of thing. It's kind of hard, but that's why you have a team to make sure.
"I get tested all the while. I got tested the day before yesterday. It's just part of the routine. "
The 26-year-old 100m and 200m world record-holder pointed to his success as a junior athlete as evidence of his innocence, reports the BBC.
"If you were following me since 2002, you would know that I've been doing phenomenal things since I was 15 years old," he said.
"I was the youngest person to win the world juniors at 15. I ran the world junior record in 19.93 at the age of 18. World youth record at 17.
"I have broken every record there is to break in every event I have ever done. I have shown I was always going to be great."
After Powell tested positive for the banned stimulant oxilofrine at the national trials last month, Bolt sent him a text message.
"I didn't want to bombard him with questions," said Bolt, who will run the 100m and 4x100m at the London Anniversary Games.
"I told him, 'Sorry to hear what was going on.' And he said, 'Yes, it's kind of rough, it's hard."'
With Gay and Powell still waiting for the results of their 'B' samples, Bolt was keen to avoid speculation when he spoke to the media in London on Thursday.
"There are a lot of details left to be discussed," he said.
The recent spate of positive drug tests has put the focus back on a sport that has been dogged by doping scandals in the past.
"It's going to set athletics back a little bit, but as a person I can't really focus on this," added Bolt.