Objective:To estimate and compare the HIV risks among three Hispanic subpopulations.Methods:Chronic drug users participating in a nationwide intervention study on drug use were interviewed with regard to drug use and sexual behavior. HIV risk was estimated using information about individuals' HIV-relevant behaviors, the social context (i.e., city) in which such behaviors occur, and published estimates of HIV transmission for various risk behaviors. Multiple linear regression analysis was used to investigate differences in estimated HIV risk between Puerto Rican, Mexican-American, and Mexican drug users, accounting for sociodemographic factors, sexual preference, and geographic region.Results:Puerto Ricans had significantly greater estimated overall HIV risk, estimated injection risk, and in general, significantly greater estimated sexual risk than Mexican Americans and Mexicans. No significant differences were found in any estimated risk between Mexican Americans and Mexicans in this sample. No significant differences were found among any of the subgroups for estimated risk from having anal sex while using a condom, or from having receptive anal sex without using a condom.Conclusions:These findings suggest that Puerto Ricans who use drugs experience a higher risk of HIV infection than other Hispanic drug users. Research is needed to identify which economic, social, and cultural components account for this increased risk.