With data from the birth registry of the Katsina Local Government Authority, the sex ratio was calculated for 1113313 Hausa children born alive between 1961 and 1980. The sex ratio was 1.07, which is significantly higher than the usually accepted value (less than 1.04) for populations of African origin. There was no seasonal variation or apparent relation to coital frequency or gonadotrophin levels. The sex ratio in another set of data comprising 5780 hospital births was 1.17 for normal and 1.31 for complicated deliveries. The sex ratio did not appear to be influenced by maternal age or parity. This set of data point to some selective bias in hospital statistics.