The pattern of acute illness was determined in 102 adolescents and adults with sickle cell anaemia who presented to the emergency unit of a Lagos hospital. The patients had a mean age of 20.5 years (SD 13.1) and a male-female ratio of 1.5. The symptoms included fever (72%), fatigue and weakness (59%), anorexia (59%) and pain (57.5%) while major clinical signs were pallor (100%), jaundice (71%) and hepatomegaly (68%). Sixty-eight per cent of patients had sickle cell crises, including one with hemiplegic stroke, 10% with combined anaemia and pain crises, 33% with anaemia crises only and 23.5% with pain crises only. Sixty-three per cent had infection which was malaria in 24.5%, bacterial in 17% and viral in 6%. Of 16 patients with pyrexia of unknown origin, seven responded to treatment with chloroquine and eight to antibiotics. Infection was detected in 50% of the patients with sickle cell crises. The association between anaemia crises and malaria was significant (P < 0.05). Of the eight deaths, seven (88%) had anaemia crises. In contrast to studies conducted two decades ago in the same hospital, the prevalence of anaemia crises now exceeds that of pain crises and malaria now exceeds that of bacterial infection. Severe symptomatic anaemia (anaemia crisis) was more frequently associated with infection (mostly malaria) than was bone pain crisis. The Girdle pain crisis more frequently resulted in a fatal outcome than the uncomplicated bone pain crisis.