While homeless men are very aware of the risk of unprotected sex, they are not very educated on how to protect themselves from sexually transmitted diseases, a USC study found.

Researchers interviewed dozens of men on Skid Row in downtown Los Angeles to understand how they viewed the risks of sexual encounters with women.

While more than half of the respondents had been tested for HIV, most held medically inaccurate beliefs they used to judge their partner's chances of having a sexually transmitted disease.

The men took into account everything from a woman's reputation and the location of the encounter to a woman's flirtiness and her earwax buildup to decide if a condom was worth the trouble, said corresponding author, Suzanne L. Wenzel of the USC School of Social Work.

"Homeless men tend to be aware of the risk for STDs but many base their actions on visual cues and other erroneous ideas about sexual health," Wenzel said. "Accurate information and education could impact the health of this at-risk population. A recent HIV test is an appropriate way to gauge risk."

The study, published in the journal AIDS and Behavior this month, concluded education has the potential to change the practices of homeless men because the participants were trying to gauge the health implications in such relationships.

The study could impact a large population as the number of homeless men in the United States is estimated to be at around 3 million and growing. The study has implications beyond the male subjects, as women are most likely to get HIV from a male partner, Wenzel said.

Men used six categories to identify risk of catching a sexually transmitted disease from a woman: obvious drug use, prostitution, mental illness, promiscuity, decency and dangerous behavior, such as belonging to a gang or selling drugs.

Homeless men are not alone in their lack of judgment or education, as other studies have reported that college students, adolescents and others use intuitive feelings of trust, appearance and perceptions of relationship seriousness when judging whether or not to use a condom, Wenzel said.

Wenzel, the principal investigator of the grant from which the study was produced, and her colleagues at the RAND Corporation have been researching health issues in homeless populations for a decade and have published more than 25 papers on HIV/AIDS, behavioral health and violence among homeless women, youth and men.

Ryan A. Brown of RAND was the lead author. David P. Kennedy, Joan S. Tucker, Daniela Golinelli, Samuel R. Werthheimer and Gery W. Ryan, also of Rand, were contributing authors.

The study was funded by the National Institute of Child Health and Human Development.