The pattern of illness in 60 consecutive children with homozygous sickle cell disease who attended the Paediatric Emergency Room of a busy Lagos hospital with acute illness was studied prospectively. Their ages ranged from 3 months to 13 years with a peak in the 2nd year. There were twice as many boys as girls. The commonest symptoms were fever, limb or abdominal pain and cough, and the commonest signs were pallor and hepatomegaly. Painful crises occurred in 27, anaemic crises in 11, and a combination of these in 12 children. Infection was detected in 76% of subjects in crises. Infection was found in 82% of all the children and was mainly bacterial. The commonest infections were pneumonia (35%), bacteraemia (32%), tonsillitis/pharyngitis (17%) and osteomyelitis (8%). The predominant bacteria isolated were Klebsiella spp (38%), E. coli (23%), Staph. aureus (23%), Staph. albus (23%) and Pseudomonas spp (23%). Some children had multiple isolates. Bacterial infection was a major cause of morbidity in very young children and merits appropriate control and preventive measures in this age group. The spectrum of bacteria isolated makes it unlikely that the specific anti-pneumococcal measures widely advocated in Europe and America for young children with SCA would be appropriate in Nigeria.