Haemoglobin DIbadan (beta 87 threonine leads to lysine) was originally found in Ibadan, an area with a high incidence of sickle cell haemoglobin (HbS). Since haemoglobin D and S are indistinguishable by most common conventional methods, the geographical coincidence of the two haemoglobin poses a serious screening problem which was investigated in the propositus who is heterozygous for S and D, his wife who is heterozygous for A and S, and their six children. The combined techniques of haemoglobin solubility, sickling rate, shaking test and routine electrophoresis have yielded an unequivocal diagnosis of the haemoglobin types of the family both for identification and quantitative estimation of the percentage of haemoglobins in the heterozygotes. HbD was found to be slightly less soluble than HbA but otherwise normal blood from S+D individuals was found to contain 57-60% HbD suggesting an increased systhesis of HbD relative to S, whereas A+D heterozygote has 41% HbD suggesting a diminished synthesis of HbD relative to HbA. The physicochemical characteristic of HbD and the haematological data in simple heterozygotes are normal.