EXPLORE: A Randomized Clinical Trial of the Efficacy of a Behavioral Intervention to Prevent Acquisition of HIV among Men who have Sex with Men (MSM)

Study Summary

What was HIVNET 015 (EXPLORE)?

HIVNET 015 was the first study to test a behavioral intervention specifically for men who have sex with men (MSM) over an extended period of time using HIV infection as the primary endpoint.

Who participated in the study?

4,295 HIV-negative MSM were enrolled in six U.S. cities: Boston, Chicago, Denver, New York, San Francisco and Seattle

What happened during the study?

Following enrollment, study participants in the standard treatment arm underwent HIV testing, received HIV-prevention counseling and completed extensive questionnaires regarding sexual behaviors, alcohol and drug use, and occurrence of sexually transmitted diseases every six months. Study participants in the intervention treatment arm completed the same activities as those in the standard arm, but they received additional counseling in the form of multiple intensive behavioral counseling sessions (with motivational interviewing and cognitive behavior theory, for example, as key components) during the first three to four months of their study involvement period. Afterward, participants received "booster" sessions every three months (for up to, on average, 3.25 years).

Why was this study important?

Many research studies had been conducted involving populations of MSM to identify interventions which can help MSM to reduce the frequency of sexual behaviors that put them at risk of getting HIV. Extensive changes in risk behaviors had occurred among MSM but, in recent years at the time of the study, HIV infections, other sexually transmitted diseases and sexual risk behaviors had been increasing, emphasizing the critical need for identifying effective prevention interventions. EXPLORE examined the potential of one such intervention to reduce HIV infection rates among MSM.


The individual factors examined were associated with sexual risk behavior. The cohort was shown to be heterogeneous in regard to the presence of combinations of these risk-related factors.

Study Documents