To analyze the general dynamics and trends of the HIV epidemic in the Dominican Republic (DR). Thorough review of available HIV seroprevalence and sexual behavioral data from the DR. Multiple sources of data suggest that the DR's HIV epidemic has generally declined. Between the mid-1990s and about 2002, HIV-1 prevalence fell among pregnant women in the capital, Santo Domingo, particularly among young women. Declines in prevalence were also observed over the same period among sexually transmitted infection clinic patients, blood bank donors, US entry visa applicants, and female sex workers. National household surveys found 1.0% (confidence interval: 0.9% to 1.1%) adult prevalence in 2002 and 0.8% (0.6% to 0.9%) in 2007. Among largely Haitian immigrant residents of the impoverished former "sugarcane plantations," prevalence was much higher but declined from 5.0% to 3.2% between 2002 and 2007. The DR's heterogeneous epidemic includes an important men-having-sex-with-men (MSM) and bisexual component. The proportion of reported AIDS cases among men remained constant from 1989 to 2006, accounting for about two thirds of both total cumulative and year 2006 cases. Some survey and qualitative data also suggest a considerable occurrence of MSM-related risk behaviors. HIV prevalence remains relatively high in MSM, with no evidence of significant decrease. As in several other developing countries that have succeeded in slowing HIV transmission, HIV reductions in the DR seem mainly due to changes in sexual behavior, particularly increased condom use, especially for sex work, and partner reduction in men. Similarly favorable HIV declines and reported behavior change have occurred in some other Caribbean countries, including neighboring Haiti. However, of concern is that anal sex, both male-male and heterosexual, remains a taboo yet apparently common practice largely ignored by existing prevention campaigns. And although the DR epidemic has generally stabilized, there is a danger of complacency, and some recent data suggest that HIV prevalence is no longer declining (and may even be increasing) in some populations.