including male-to-male sexual contact, intravenous drug use, and heterosexual contact with an injection drug user. The seroprevalence rate in individuals denying these risks was 3.6 percent in men (50 of 1,389) and 4.2 percent in women (22 of 522). Among women, the behaviors associated with infection were prostitution and the use of crack, and among men, a history of syphilis, crack use, and sexual contact with a crack-using sex worker were associated with HIV infection.

The potential for a male in sex-for-crack exchanges to come into contact with an HIV-positive female partner was demonstrated in a study of 87 New York City women who had been admitted to a municipal hospital with a diagnosis of pelvic inflammatory disease (Des Jarlais, Abdul-Quader, and Minkoff, 1991). Crack use was reported by 56 percent of the subjects (n = 49), and of these, 20 percent were HIV positive. Crack use was significantly related to both traditional AIDS risk behaviors (injecting drugs and having sex with an injection drug user) and other unsafe sexual behaviors (exchanging sex for money or drugs and having casual sex partners).

Given the potential for sex-for-crack exchanges to spread HIV to new populations, in 1989 NIDA began supporting ethnographic studies of the phenomenon in eight cities—Chicago, Denver, Los Angeles, Miami, Newark, New York, Philadelphia, and San Francisco (Ratner, 1993). A total of 340 crack users (69 percent of whom were women) were interviewed in depth. Of the 233 women, 108 had participated in sex-for-crack exchanges, as had 69 of the men. HIV testing was done with 168 of the subjects, and a total of 14 percent were found to be positive for HIV antibodies. Of the 24 males who were non-injectors and who had engaged in heterosexual sex-for-crack exchanges, 3 were HIV positive.

Only very recently has the possible link between alcohol consumption and risky sexual behavior been explored in the context of HIV transmission. This is somewhat surprising, given that it is a fairly common belief that alcohol use and risky sexual behavior are causally linked. Alcohol is perceived to reduce inhibitions, causing impulsive or out-of-control behavior and thereby increasing the likelihood of risky sexual activity. Nevertheless, despite this widespread—and intuitively appealing—belief, direct causality of alcohol use and risky sexual behavior has not been established.