A study to measure adherence to artesunate and amodiaquine (AS+AQ) therapy in patients treated for uncomplicated malaria in community health centres (CHC) was conducted in Sierra Leone. Patients/caretakers were interviewed and remaining AS+AQ tablets at home after the last treatment dose were counted. Persons leaving CHCs with an AS+AQ prescription were also interviewed (exit interviews). In total, 118 patients were visited at home: 27 (22.9%) had one or more tablets left and were classed as certainly non-adherent; 34 (28.8%) were probably non-adherent [reported incorrect (n=27) or incomplete (n=7) intake]; and 57 (48.3%) were probably adherent. The main reasons for incomplete intake were sickness after one dose of AS+AQ, no food available for drug intake and forgetting to take them. For incorrect intake, reasons were vomiting after drug intake and incorrect instructions given by the CHC. Eighty-one percent of probably adherent patients reported following instructions given to them. In exit interviews, 82% of patients or caretakers of patients were able to repeat AS+AQ intake instructions correctly. Adherence to antimalarial treatment should not be taken for granted. Instructions on correct AS+AQ use should include discussion of disease symptoms as well as possible treatment side effects and how to manage them. Other factors are more difficult to influence, such as patients forgetting to take the treatment.