In the past decade, Cambodia has been experiencing the most serious HIV/AIDS epidemic in Southeast Asia. With full support from the top policy makers, good leadership in program management, and the commitment of the public health program officers, the HIV/AIDS prevention and care program in Cambodia has been successful, despite its resource constraints. Available data from surveillance and other studies in Cambodia indicate a downward trend in HIV prevalence and incidence among high-risk groups, an increase in condom use among commercial sex workers and their clients, and a declining trend of sexually transmitted infections. Although these findings reflect the success of programs to prevent transmission, the incidence of HIV infections is still high in high-risk populations, and transmission among the general population continues. Cambodia therefore needs to increase its efforts to reduce transmission. More research and prevention programs should focus on the vulnerable populations. HIV/AIDS modeling indicates that Cambodia needs to prepare for increasingly large numbers of AIDS patients who will require expensive medical care.