Background: Internalized homonegativity (IH) has been associated with increased HIV risk-behaviors among men who have sex with men (MSM). 'Invisibility' of sexual orientation, intentional 'concealment' of sexual preferences, and 'perceived discrimination' relate closely with factors of internalized homophobia or internalized homonegativity validated in previous literature. IH may operate differently for exclusive MSM than for men who have sex with men and women (MSMW). Differential effects of IH on MSM sub-groups may help explain observed inconsistencies between higher risk-behavior and lower HIV prevalence among MSMW. This dissertation explores the independent and joint effects of IH factors and gender of past sexual partners on the link between sexual risks and HIV status. Methods: A random sample of 1,111 MSM in four Mexican cities underwent HIV testing and answered a questionnaire on sexual practices and stigma against homosexuality. With these data, this study developed three scales to measure 'invisibility', 'concealment' and 'stigma/discrimination', as component factors of IH, defining the latter two scales jointly as 'internalized homonegative stigma' (IHS). Statistical analyses were conducted with SPSS 15.1. Results: 42.2% of participants reported sex with women at least once in their lifetime. Overall HIV prevalence was 10.4%, but it was significantly lower among MSMW (p=.007). Both sexual behavior and levels of IH differed between MSMW with recent women partners (MSMW-R) and those who reported past but no recent women partners (MSMW-E). MSMW of both groups reported more paid sex (p<0.001) and less receptive anal sex (p<0.001) than exclusive MSM. Adjusting for age and risk patterns, MSMW were less than half as likely to be HIV positive than other MSM; IHS influenced this relationship increasing the odds of being HIV positive across study groups, while gender of past sexual partners and 'invisibility' jointly interacted to lower the likelihood of HIV infection for MSMW-E. Conclusions: Factors of IH operate in antagonistic directions: our data suggest that HIV prevention could benefit directly from fighting stigmatizing and discriminating social attitudes, without focusing on increasing 'visibility' of MSM.