Men with larger foreskins are more likely to become HIV positive, according to a new Uganda-based study as reported by Reuters. Researchers from Johns Hopkins University’s Rakai Health Sciences Program in Uganda said their findings—published October 28 in the journal AIDS—support the argument that circumcision is a viable HIV prevention method for men.

The investigation followed 965 Ugandan men, all of whom were initially HIV negative. Researchers observed a direct correlation between foreskin size and HIV infection risk.

“Mean foreskin surface area was significantly higher among men who acquired HIV,” researchers wrote. Study authors believe that the foreskin has many immune cells called dendritic cells, and that HIV can enter the body through these cells.

While multiple studies show that circumcision helps prevent female-to-male HIV transmission, the procedure does not protect female sex partners from contracting the virus.