During the period 1975-1980, 105 infants out of a total of 116 859 delivered at selected hospitals in the Cape Town area had a neural tube defect. The combined incidence of spina bifida and anencephaly in Whites was approximately 1/300 births, which is similar to that generally encountered in the UK. However, the incidence in other ethnic groups was appreciably lower at 1/1250 and 1/2000 births for the Coloured (mixed ancestry) and Black groups respectively.