Glycosylated haemoglobin (HbA1) was determined by a microcolumn technique using Biorex 70 resin in normal Nigerians and in patients with diabetes, iron deficiency anaemia, sickle cell disease and renal failure. Mean %HbA1 was 10.0 +/- 1.9% in controls which is higher than levels reported in Caucasians. HbAS but not HbSS had a reducing effect on the %HbA1 which was also found elevated in iron deficiency anaemia and diabetes mellitus. Factors peculiar to tropical medical practice affecting glycosylated haemoglobin must be appreciated and further investigated to assess the usefulness of HbA1 determination in the long term control of diabetes mellitus.