BACKGROUND This study was carried out to determine the haematological profile and malarial parasitaemia of children requiring emergency blood transfusion. METHODS This prospective study was carried out from 1st August to 30th of November, 1999 at the Children Emergency Ward (CHEW) of the Obafemi Awolowo University Teaching Hospital (OAUTH) Ile-Ife, Nigeria. All children requiring emergency blood transfusion seen at the CHEW were included in the study. Blood samples were taken on admission for haematocrit, white cell count and differentials, thin and thick blood films. Other data recorded include age, sex, clinical impression on admission. RESULTS Four hundred children were admitted into the CHEW during the study period and 173(43%) required emergency blood transfusion. One hundred and forty-five (84%) of the children who required emergency transfusion were below the age of five years. There was no sex predilection. Although, clinical impression of malaria was made either singly or in combination with other diseases in almost all the patients, malaria parasitaemia was confirmed in 86 (50%) of the patients. The mean haematocrit was 0.14 L/L. In 60% of the children, there were mixed microcytic hypochromic and macrocytic red bloodcells. CONCLUSIONS We conclude that severe anaemia requiring emergency blood transfusion is a major cause of morbidity and mortality in under five children. We also confirm that malaria and nutritional deficiencies are the major cause of severe anaemia in Nigerian children. We therefore recommend urgent need for prevention and prompt treatment of malaria in children under the age of five years. We also recommend the need for improvement in the nutritional intake of children under the age of five.