Male circumcision, already shown to reduce the incidence of H.I.V. infection in men, also reduces transmission of both herpes simplex virus Type 2 and human papilloma virus, a study has found.

According to the Centers for Disease Control and Prevention, at least 45 million people in the United States ages 12 and older have had herpes, or H.S.V.-2, the incurable infection that can cause recurrent painful genital lesions. About 20 million are currently infected with human papilloma virus, or H.P.V., which causes various genital cancers, including most cervical cancers. There is no treatment or cure for H.P.V., but there is a vaccine now licensed only for girls and women.

The study, a randomized clinical trial published Thursday in The New England Journal of Medicine, assigned more than 3,000 uncircumcised Ugandan men who were not infected with H.S.V.-2 to undergo immediate circumcision or to be circumcised 24 months from the start of the investigation. A subgroup was similarly evaluated for H.P.V. infection.

At 24 months, 114 men of the men initially circumcised and 153 of the noncircumcised tested positive for H.S.V.-2. After controlling for various health and behavioral factors, the researchers estimated that circumcised men had a 25 percent reduced risk of infection. The results do not apply to their partners.