In contrast to rates for the United States as a whole, the incidence rate of gonorrhea increased 11% in San Francisco between 1986 and 1988, with substantial increases observed among black adolescents. Reports by health department personnel and police suggested that crack cocaine use, specifically the exchange of sex for drugs, contributed to this increase. To test this hypothesis, the authors conducted a case-control study from August 1988 to October 1988 that compared 68 prospectively identified adolescent gonorrhea patients with 136 neighborhood control patients. Thirty-two percent of the female gonorrhea patients had received money or drugs in exchange for sex, while none of the control patients reported having done so (P = 0.0001). Most of the female patients (89%) who had received money or drugs in exchange for sex had used crack. Crack use was less common among female patients who denied receiving money or drugs in exchange for sex (11%) and among control patients (6%). Crack use and providing money or drugs in exchange for sex were not risk factors for gonorrhea among the male patients, but were reported frequently by both gonorrhea patients and control patients. Not living with parents was a risk factor for male patients (odds ratio 4.9, 95% confidence limit 1.4 to 19.5). For all patients, a history of a sexually transmitted disease appeared to be an independent risk factor for gonorrhea. The conclusion is made that crack-related exchange of sex for money or drugs is a risk factor for gonorrhea among black adolescent girls in San Francisco.(ABSTRACT TRUNCATED AT 250 WORDS)