Circumcision may provide even more protection against AIDS than was realized when two clinical trials in Africa were stopped two months ago because the results were so clear, according to studies being published today.

The trials, in Kenya and Uganda, were stopped early by the National Institutes of Health, which was paying for them, because it was apparent that circumcision reduced a man’s risk of contracting AIDS from heterosexual sex by about half. It would have been unethical to continue without offering circumcision to all 8,000 men in the trials, federal health officials said.

That decision, announced on Dec. 13, made headlines around the world and led the two largest funds for fighting AIDS to say they would consider paying for circumcisions in high-risk countries. But the final data from the trials, to be published today in the British medical journal The Lancet, suggest that circumcision reduces a man’s risk by as much as 65 percent.

The December announcement described only the follow-up on the men as originally divided into two groups: those who agreed to be circumcised and those who agreed not to. But some in the first group never went to the circumcision clinic, and some in the second had private circumcisions before the study ended.