Summary.A total of 150 blood samples tested for serum albumin and transferrin and for red cell carbonic anhydrase, phosphoglucomutase, phosphogluconate dehydrogenase, phosphohexose isomerase, nucleoside phosphorylase, acid phosphatase, ‘X’‐protein and potassium concentration only showed variation at the ‘X’ protein and nucleoside phosphorylase loci. Isoelectric focusing over pH range 6–8 showed 145 samples to be of haemoglobin type A and 5 type AD. The haemoglobin A type was resolved into further types by separation over pH 6.9–7.5 in Immobiline polyacrylamide gels. A 2‐ or 4‐band pattern was present in 136 of the samples; a genetic hypothesis based on four or more different haemoglobin A variants is proposed. 14 samples had a 3‐, 5‐ or 6‐band pattern. It is assumed that these are heterozygous for a