One hundred and forty adult patients who had at least one unit of group compatible and / or group identical blood were studied for the development of acute haemolytic transfusion reaction after transfusion. Group identical transfusion was the commonest form of transfusion in the study. Eighty patients (57.1%) had group identical transfusion while sixty patients (42.9%) had group compatible transfusion. The following tests and parameters were measured in the pre and 6 hours post transfusion samples: Changes in PCV, intravascular agglutinates, colour of plasma, haemoglobin and bilirubin concentrations, and Direct Coomb’s Test (DCT). Clinical parameters like fever, throbbing headache, chest tightness, jaundice, heat in the vein, and lumbar pain were monitored. Blood pressure and heart rate were recorded. None of the patients had laboratory evidence of acute (immune) haemolytic transfusion reaction based on the result of Direct Coomb’s Test and intravascular agglutinates. One patient (0.7%) in the group compatible transfusion group had clinical signs and symptoms suggestive of acute haemolytic transfusion reaction (jaundice and chest tightness), with elevated levels of plasma haemoglobin and bilirubin concentrations. But she lacked serological confirmation in that the result of her DCT was negative and there were no demonstrable intravascular agglutinates in her plasma after the transfusion. There was statistically significant difference in the changes in PCV between the group compatible and the group identical blood transfusion recipients. Group identical transfusion was more associated with higher increament in PCV than group compatible type. The two types of transfusions were not associated with significant haemolytic transfusion reaction. Because of the low level of donor bloodstocks in the UITH and other blood banks in Nigeria, group compatible transfusion will continue to play major role in transfusion practice in this country.