Abstract
1. The literature of primary or idiopathic protrusio acetabuli is reviewed with particular reference to familial and racial influence on pathogenesis.
2. The radiological criteria of a "deep" acetabulum and of a "protruded" acetabulum are discussed.
3. Four generations of a family are presented in which all three members of the second generation showed marked protrusio acetabuli. In the remaining generations most members appeared to have abnormally deep acetabuli.
4. It is concluded that this family shows a strong familial tendency to deep or intruded acetabuli. The family tree, though incomplete, suggests a genetic influence ofa dominant type.