WHO officials are concerned that traditional healers might try to provide circumcision without adequate training and without providing counseling on how to prevent AIDS.

The study, conducted in South Africa, found that circumcision reduced the risk of men contracting AIDS during heterosexual intercourse by about 65 percent.

"There had always been a suspicion that male circumcision prevented AIDS ... but this is the first randomized study using control trials," said Dr. Bertrand Auvert, who coordinated the study for France's National AIDS Research Agency.

Auvert announced the finding at the Third International AIDS Society Conference on HIV Pathogenesis and Treatment in Rio de Janeiro, which ends Wednesday.

Effect of Circumcision

The study was conducted between 2002 and 2005 with more than 3,000 healthy, sexually active males between 18 and 24 in Orange Farm, South Africa, where about 32 percent of the female population was HIV positive.

For the study, about half of the subjects were circumcised by medical professionals, and the rest remained uncircumcised.

All of the men received counseling on AIDS prevention. But after 21 months, 51 members of the uncircumcised group had contracted HIV, the AIDS virus, while only 18 members of the circumcised group had gotten the disease.

Circumcision "prevented six to seven out of 10 potential HIV infections," said Auvert.

He said the study did not analyze the effect of circumcision on male-to-female transmission or if circumcision provides effective protection over the long term. At least three more studies are under way to confirm the effectiveness of circumcision.

Guarded Optimism

But scientists said the study was cause for guarded optimism.

"While these results are very promising, we need to put them in a broader context to see the full benefits of circumcision. So we need to look at results from other studies," said Dr. Charles Gilks, director-coordinator of treatment and prevention for the World Health Organization.

A study funded by the US National Health Institute involving 5,000 individuals is currently under way in Uganda. Scientists expect to announce the results only in early 2007.

Gilks said he was concerned that the results of the study would lead many circumcised men to think they were protected from AIDS and fail to take adequate precautions.

He also worried that it would lead many men to rush to get circumcised, and said the World Health Organization was racing to set guidelines for safe and hygienic circumcision.

Sensitive Issue

Gilks said his main concern was that traditional healers might try to provide circumcision without adequate training and without providing counseling on how to prevent AIDS.

In the Orange Farm study, where the circumcisions were carried out by medical professionals, about 4 percent of patients suffered minor complications.

Catherine Hankins, chief scientific adviser to UNAIDS, said that it was still too early to encourage widespread circumcision as a way to prevent the spread of AIDS. And she said many men would resist circumcision, even if other studies confirmed the findings.

"We know this is a sensitive issue, and I don't just mean biologically," Hankins said.