In an anthropological investigation of 114 Bengalee families of the Sodepur industrial suburb of Calcutta, the average haemoglobin level is found to be significantly lower in males with A1 blood group than those with other blood groups, and this is more marked in young age. A depression of the haemoglobin level is also apparent in women of reproductive age who have blood group O, conforming to the suggestion of greater bleeding tendencies in individuals with·blood group than in others.