One afternoon last month at a safe sex workshop in San Antonio, John Barbo tore into a box of condoms and slipped one over a dildo. There are two different ways to do this, he told a dozen or so men who have sex with men (MSMs), depending on whether the penis is circumcised or not… Huh? Circumcised or not? A 32-year-old African-American man in the room was confused: Can’t circumcised men skip condoms altogether and still prevent HIV transmission? Isn’t that what he heard the other day on the news?

Not exactly. Foreskin or no foreskin, tossing your Trojans is not an option. New studies in Sub-Saharan Africa do show that circumcision reduces the risk of HIV infection in men having vaginal sex with positive women by up to 60 percent—a major finding that is being hailed around the world as the biggest prevention breakthrough since microbicides. But some people are getting the wrong idea. “Statistically [circumcision] does reduce the risk, but calling it a prevention method sends a mixed message,” says Barbo, who used his group member’s confusion that afternoon at San Antonio’s BEAT AIDS as an excuse to put the science in context for the whole crowd: Circumcision isn’t HIV prevention but a form of harm reduction—one tool among many recommended for lowering overall risk for certain people.

Clearing up the mixed message about circumcision is a top concern now for prevention experts not just in U.S. cities and towns where TV and newspapers delivered the dramatic foreskin news last month with great fanfare—but all around the world. “People should be thinking that this is an important development, but it’s not the magic bullet,” says Paul Zeitz, MD, of Global AIDS Alliance. Adds Carolyn Williams, PhD, at the National Institutes of Health, “Circumcision is a good option [to further reduce the risk of HIV transmission], but it’s not a substitution for anything that’s been in the prevention package before.”

This week, health experts are holding a special United Nations meeting in Montreux, Switzerland, to clear up some of the confusion before it snowballs. The main challenges: How to ensure that people don’t see circumcision as a free pass for having unsafe sex; and how to promote circumcision even though conducting the procedure in sub-standard health care settings can sometimes encourage HIV infection, a concern that was at the heart of a cautionary study released just last week.

Prevention experts point to the limitations of the African data: No one has looked yet at circumcision’s effects on anything but female-to-male transmission. “We’re encouraging further research because we need to know how effective circumcision may be for [preventing HIV transmission to straight women], gay men and anyone who engages in anal sex,” says Judith Auerbach, PhD, of the San Francisco AIDS Foundation.

And what do the African findings mean for Americans per se? In the U.S., approximately 80% of men are already circumcised, mostly at birth, and only 15% of new HIV infections are from heterosexual sex. Circumcision is a painful procedure for adults to endure; is anyone really sure it’s worth going through?

Among the goals of this week’s U.N. meeting are setting hygienic standards such as sterilizing equipment before performing circumcisions and drafting strategies to make sure that men don’t have sex until their penises have time to heal.

“We need to make sure that [circumcision is] done in an optimal way so that there is no risk of transmission,” says Zeitz, who is particularly concerned that, with all the fuss in Africa now about circumcision being advantageous, traditional practices may escalate before the U.N. gets a chance to establish these standards. Not to mention the trickiness of implementing them in areas of the world, such as tribal Africa, where circumcision may be a rite of passage and outside advice is simply not welcome.

John Barbo’s concerns about delivering the circumcision news in San Antonio are closer to Africa’s prevention predicaments than you might think. Even in the most equipped U.S. health care setting, it’s not a simple message. “We have a bad enough problem with HIV spreading,” he says. “Telling people to get circumcised just creates more.”