Behavioral interventions reduce self-reported unprotected anal sex among MSM. These results indicate that HIV prevention for this population can work and should be supported. 
Results of previous studies provide a benchmark for expectations in new studies. Meta-analysis can inform future design and implementation in terms of sample size, target populations, settings, goals for process measures, and intervention content.
When effects differ by design variables, which are deliberately selected and planned, awareness of these characteristics may be beneficial to future designs. Researchers designing future small group and individual-level studies should keep in mind that to date, effects of the greatest magnitude have been observed in studies that used count outcomes and a shorter intervention span (up to 1 month).
Among small group and individual-level studies, effects were also greatest when the comparison condition included minimal to no HIV prevention content. Nevertheless, statistically significant favorable effects were also seen when the comparison condition included standard or other HIV prevention content. Researchers choosing the latter option for new studies should plan for larger sample sizes based on the smaller expected net intervention effect noted above.
When effects differ by implementation variables, which become evident as the study is conducted but are not usually selected or planned, caution may be advised so that future studies can reduce bias. Because intervention effects were somewhat stronger (though not statistically significantly so) in studies with a greater attrition in the comparison condition, differential retention may be a threat to validity. Extra effort should be given to retaining participants in comparison conditions.
Among community-level interventions, intervention effects were strongest among studies with random assignment of groups or communities. Therefore the inclusion of studies where assignment of groups or communities was by convenience did not exaggerate the summary effect. The greater effectiveness of interventions including more than 25% non-gay identifying MSM suggests that when they can be reached, these men may be more responsive than gay-identified men to risk reduction efforts. Non-gay identified MSM may have had less exposure to previous prevention messages, so their initial exposure may have a greater impact.
The greater effectiveness of interventions that include efforts to promote personal skills such as keeping condoms available and behavioral self-management indicates that such content merits strong consideration in development and delivery of new interventions for MSM. And the finding that interventions were most effective for majority white populations underscores the critical need for effective interventions for MSM of African and Latino descent.
Further research measuring the incidence of HIV and other STDs is needed. Because most studies were conducted among mostly white men in the US and Europe, more evaluations of interventions are needed for African American and Hispanic MSM as well as MSM in the developing world. More research is also needed to further clarify which behavioral strategies (e.g., reducing unprotected anal sex, having oral sex instead of anal sex, reducing number of partners, avoiding serodiscordant partners, strategic positioning, or reducing anal sex even with condom use) are most effective in reducing transmission among MSM, the messages most effective in promoting these behaviors, and the methods and settings in which these messages can be most effectively delivered.
Changing sexual behavior among gay male repeat testers for HIV: a randomized, controlled trial of a single-session intervention.
High-risk sexual behavior is increasingly prevalent among men who have sex with men (MSM) and among men with a history of repeat testing for HIV.
                The study assessed whether one counseling intervention session focusing on self-justifications (thoughts, attitudes, or beliefs that allow the participant to engage in high-risk sexual behaviors) at most recent unprotected anal intercourse (UAI) is effective in reducing future high-risk behaviors among HIV-negative men.
                A randomized, controlled, counseling intervention trial was conducted at an anonymous testing site in San Francisco, California, between May 1997 and January 2000. Participants were 248 MSM with a history of at least one previous negative HIV test result and self-reported UAI (receptive or insertive) in the previous 12 months with partners of unknown or discordant HIV status. Two intervention groups received standard HIV test counseling plus a cognitive-behavioral intervention, and two control groups received only standard HIV test counseling. Follow-up evaluation was at 6 and 12 months.
                Number of episodes of UAI with nonprimary partners (of unknown or discordant HIV status) in the 90 days preceding the interview was measured via self-report during face-to-face interview.
                A novel counseling intervention focusing on self-justifications significantly decreased the proportion of participants reporting UAI with nonprimary partners of unknown or discordant HIV status at 6 and 12 months (from 66% to 21% at 6 months and to 26% at 12 months, p =.002; p <.001) as compared with a control group when added to standard client-centered HIV counseling and testing.
                A specific, single-session counseling intervention focusing on a reevaluation of a person's self-justifications operant during a recent occasion of high-risk behavior may prove useful in decreasing individual risk behavior and thus limiting community-level HIV transmission.