Background The association between general patterns of alcohol intake and sexual risk behaviours among men who have sex with men (MSM) and transgendered women (TW) populations has been well- established. However, there is limited event-level data on alcohol use and contact-specific risk behaviour from low resource settings with MSM/TW-concentrated HIV epidemics such as Peru.

Methods We performed secondary analysis of baseline data from a community-based HIV prevention trial with MSM/TW subjects from 24 neighbourhoods (clusters) in urban Lima. Using multivariate Poisson regression with standard errors estimated for clustered data to calculate prevalence ratios (PR), we measured the adjusted association between situational drinking and unprotected anal intercourse (UAI) during the subject’s last sexual contact.

Results A total of 718 subjects were included (Mean age = 29, Range = 18–45; 71.1% MSM and 28.9% TW), of whom 63.3% had engaged in transactional sex during the previous year. Overall, 45.4% of subjects reported UAI with their most recent partner, and 46.1% reported alcohol intake before their last sexual encounter (drinking either with or without him/her). In multivariate analysis, participants were more likely to practise UAI in the last sexual encounter with their last partners if they drank alcohol before sex (PR = 1.23, 95% CI: 1.03–1.47), after adjusting for age, education, sexual identity, sexual role, number of partners over the last year, transactional sex during the previous year and partner type (stable, casual, or transactional sex partner).

Conclusions The independent association between contact-specific alcohol consumption before sex and UAI among MSM/TW in Peru warrants further in-depth exploration to understand the exact mechanisms and determinants of these two behaviours at individual-, partner- and community-levels. Interventions to reduce sexual risk behaviours should address situational drinking among MSM and TW populations.