Of the 42 million living with HIV/AIDS world-wide some 90% live in developing countries. The international community acknowledges the devastating impact of HIV/AIDS on development and over the past few years resources to control HIV/AIDS have increased considerably. We argue that strengthening of health systems is a necessary prerequisite for improving the prevention of HIV infection and the care of HIV-infected persons. Sexual behaviour change requires a multidisciplinary approach, but health services play a crucial role in detection and treatment of other sexually transmitted infections; HIV counselling and testing; prevention of mother-to-child transmission of HIV; and care of HIV-infected patients. Increasing access to antiretroviral treatment especially poses formidable challenges to health authorities in developing countries. Additional resources for the prevention of HIV-infection and the care of HIV-infected persons may not have the desired impact if health systems in developing countries are not strengthened. Further, any activity in the area of HIV/AIDS prevention and care, carried out within health services, can have a positive ripple effect on other health care activities and vice versa. This interactive effect needs to be acknowledged and built on.