A 5-year prospective study of 4,934 children of different ethnic groups has demonstrated a 3-fold increase of postneonatal mortality and childhood morbidity in the offspring of consanguineous Pakistani parents. Most of these families contained more than one consanguineous union, resulting in a mean inbreeding coefficient for their children of 0.0686. It is estimated that 60% of the mortality and severe morbidity of this group of children could be eliminated if inbreeding ceased. However consanguinity is much favoured in this minority group, and health education will have to be carefully and sensitively handled.