The clinical findings in 11 families with 52 members affected with the Waardenburg syndrome (WS) are presented and compared with the findings from other studies. The families are assigned to WS type I (7 families containing 31 affected individuals), or type II (4 families with 21 affected members), depending on the presence or absence of dystopia canthorum, and the differences between the two types are discussed. The hypothesis that the features of WS are explicable on the basis of a neural crest defect is supported. Attention is drawn to the finding of spina bifida in 2 unrelated WS type I patients, and of delayed milestones or poor school performance necessitating special schooling in 9 different unrelated patients. Deafness has previously been considered to be the most disabling characteristic of the condition, but if there is an increased incidence of spina bifida or mental retardation associated with WS, the approach to genetic counselling might need to be altered.