OBJECTIVE: To determine whether HIV testing and posttest counseling may be associated with an increase in gonorrhea incidence among adolescents and young adults seen at a clinic for sexually transmitted diseases (STD). DESIGN: A historical cohort study with the collection of longitudinal data on the patients' HIV testing and counseling experience. SETTING: Delgado STD clinic of New Orleans, Louisiana, a public ambulatory primary care center that serves mainly the economically disadvantaged Black population. PATIENTS: A record-based inception cohort of 4031 patients aged 15-25 years diagnosed at the clinic between June 1989 and May 1991 with a first lifetime gonorrhea infection. INTERVENTION: Routine confidential HIV tests and posttest counseling sessions experienced at the clinic during follow-up. OUTCOME MEASURE: Incidence rate of reported gonorrhea reinfection. RESULTS: Of the patients, 51.5% were tested once for HIV antibodies and 25.9% twice or more. Formal posttest counseling occurred after 8.5% of the 4665 HIV-negative and 44.0% of the 49 HIV-positive tests. In the most pessimistic of several models controlling for history of gonorrhea, HIV testing and counseling history, and other potential confounding factors, a significantly lower rate of gonorrhea reinfection was observed after a first HIV-negative test than before [adjusted relative risk (RR), 0.66; 95% confidence interval (CI), 0.59-0.74; P < 0.00011. As compared with the pretest period, significantly higher rates of gonorrhea were observed after respectively a second (RR, 1.18; 95% CI, 1.01-1.37; P = 0.03) and a third (RR, 1.52; 95% CI, 1.22-1.88; P = 0.0001) HIV-negative test. No significant association was found between HIV-positive testing and any variation in gonorrhea rate (RR, 0.95; 95% CI, 0.56-1.62; P = 0.85). Posttest counseling for HIV-negative and HIV-positive results were followed respectively by a significantly higher rate of gonorrhea (RR; 1.27; 95% CI, 1.09-1.48; P = 0.002) and a non-significantly lower rate of gonorrhea (RR, 0.53; 95% CI, 0.17-1.60; P = 0.85). CONCLUSION: Our results do not exclude the possibility of a modest increase in gonorrhea incidence after routine HIV testing and counseling in an STD clinic. Nevertheless, this conclusion holds only under the least favorable assumptions and applies solely to a minority of patients.