catchment area. Patients who cannot be adequately cared for at the community centre are transferred to the district hospital in Kaengkhoi, which is staffed by internists, paediatricians and surgeons. Patients who require subspecialty services or therapies not available in the district hospital are transferred to the provincial hospital near Kaengkhoi. Some doctors working at government hospitals earn extra income by seeing patients at their private clinics in the evenings. A survey conducted in 2000 identified 16 private clinics in the study area. Not all patients seek care at public or private clinics; some patients treat themselves with over-the-counter pharmaceuticals or traditional products. Residents are assigned to government health centres, which may be the community health centre or the out- patient department of a hospital. Government policy encourages patients to see their assigned primary health-care provider by charging reduced fees for seeing the assigned provider. All community health centres in the study area, the district hospital and the provincial hospital participated in the surveillance study.