A group of about 700 patients was recruited who have been on ART for up to 7 years. This unusual follow-up group provides an opportunity to address questions about the long term effects of ART with respect to HIV disease and treatment side effects. Such effects may differ from those seen in the North because of genetic characteristics, type of ART regimen received, differences in treatment adherence, or due to other diseases typical for Africa. We will also make use of this group for a trial to investigate the safety of stopping cotrimoxazole prophylaxis in patients doing well on ART (this is a drug that prevents bacterial infections in patients with weak immune system and may no longer be needed in patients who regained their immunity due to ART). We will also explore whether nurses (rather than doctors) can provide routine follow up care for ART patients (which would be important for areas where there is no doctor), or whether larger intervals between drug refills (e.g. 3 months versus 1 month) are safe in managing patients. - We also keep regular contact with patients who have been HIV infected for a long time, but who are still well and do not need ART yet. This group is important for research on the immunological factors that may protect individuals from becoming HIV infected at all or infected individuals from experiencing fast diseases progression. Such knowledge may be helpful for the design of an effective vaccine against HIV infection.