One-hundred-and-sixty-six episodes of fever in 162 children with sickle cell anaemia (SCA) aged 6 months to 16 years, presenting to the children emergency room of the University of Benin Teaching Hospital, Nigeria with rectal temperature greater than or equal to 38.3 degrees C were studied for malarial parasitaemia. Non-sicklers of similar ages and with similar temperatures were also studied as controls. Malarial parasitaemia was documented in 9 per cent of children with sickle cell anaemia, and 29 per cent of controls (P less than 0.0001). Bacteraemia occurred in 33 per cent of children with SCA and 26 per cent of controls (P greater than 0.10). Bacteraemia was, therefore, the commonest cause of pyrexia in febrile children with sickle cell anaemia on antimalarial prophylaxis. It is suggested that children with SCA on regular anti-malarial prophylaxis who present with significant pyrexia should be carefully screened for bacterial infection and appropriate anti-microbial therapy instituted.