Further note on possible changes in the geographic distribution of ABO and RH blood groups in Great Britain.

We previously reported the tendency for the clines of blood group distributions in England, Scotland, and Wales to become flatter as the result of internal migration. The data came from a one-week birth cohort followed for 16 years. A further seven years and a finer geographic analysis yield mixed results. The Rh- clines did become flatter, but the clines for ABO blood groups A and O showed the opposite tendency during the additional years.