"What counts is that we act against this evil drug use," the president of the International Olympic Committee (IOC) said.
"Every positive test catches a cheat and protects a clean athlete. Today everybody knows we mean business. We have got zero tolerance to drug use and we are doing all we can." Nine athletes have been excluded from the Games for testing positive in IOC tests for banned substances ranging from stimulants to anabolic steroids.
A further four - including Greek sprinters Costas Kenteris and Katerina Thanou - fell foul of doping violations by being unavailable for testing or refusing to provide samples.
The International Weightlifting Federation has also suspended seven of its athletes for failing tests. "We think people want to know what or who is credible at the Olympic Games," Rogge said.
"We are making major progress against doping because it is becoming more and more difficult to cheat at the Olympic Games.
"The fact that many tests are being manipulated is proof that the tests work." Rogge said he was confident athletes could no longer get away with tampering with samples.
"Samples of blood or urine must be produced under visual scrutiny," he said. "If we have any doubts at all we can still do a DNA analysis to match the sample to the athlete. We haven't needed that so far but it is there if we need it."
The withdrawal of Greek 200 metres Sydney Olympics champion Kenteris from the Athens Games and that of his training partner 100 metres sprinter Thanou cast a dark shadow over the first week of the Olympics.
Kenteris pulled out of the Games after missing a drugs test in mysterious circumstances the day before the opening ceremony.
He has denied taking banned substances and says he was never informed of an appointment with doping officials.
Many Greek athletes have come out in support of Kenteris and Thanou and on Thursday booing from the crowd held up the 200 metres final. But Rogge said he was sure the IOC had done the right thing.
"There has been an emotional reaction here and there but sport is about passion and you will never stop that."
Rogge said viewing figures bore out his opinion that the fight against doping must be paramount.