Haemoglobin Manukau (beta 67 Val-->Gly) is a novel haemoglobin variant presenting in two brothers as nonspherocytic haemolytic anaemia which became transfusion dependent by 6 months of age. The severity of clinical expression seems to be modulated by coexisting alpha thalassaemia: the severely affected children have a normal complement of alpha globin genes with an unusual genotype (-alpha 3.7/alpha alpha alpha 3-7), while their father, who carries the abnormal gene with minimal symptoms, has homozygous alpha+ thalassaemia (-alpha 3.7/-alpha 3.7). Another unusual feature of this case is the association of the beta 67 Val-->Gly mutation with modification of beta 141 Leu to a residue (believed to be hydroxyleucine) that is not detected by standard amino acid analysis. This finding offers an explanation for the previous report of an association of another mutation at this site (Hb Sydney beta 67 Val-->Ala) with Hb Coventry (deletion of beta 141 Leu).