According to the most extensive and rigorous studies of the connection between circumcision and HIV transmission (the results are as-yet unpublished, but they've been widely discussed in the HIV prevention community, apparently), circumcision reduces a man's likelihood of infection from intercourse with an HIV-positive woman by as much as 70%.
The research project is one of three taking place in Africa (this one was in South Africa; the other NIH studies are in Kenya and Zaire.), and it was ended early, presumably because the results were so definitive.
Can you imagine what Americans would do if a group of foreigners blew into town and tried to round up 3,000 men to be randomly circumcised? But then, South Africa IS a country where people actually believe you can prevent HIV by having sex with an infant, so go figure.]
While these medical results--if they're published and validated--may help some parents decide whether to have their baby boys circumcised, conservatives face a dilemma about what to do: on the one hand, the story's in the Wall Street Journal; but on the other, the study was conducted by the French.