SINCE the original descriptions of nemaline myopathy in 1963 by Shy et al1,2in a four-yearold girl with pelvic and pectoral girdle weakness, other cases from different families have been described.3-5In none of these cases have muscle biopsies proved involvement of other members of the family with an exact disease process. The present study is concerned with the clinical features and the pathological changes in the muscles of the first proved cases of nemaline myopathy occurring in two generations of the same family. Report of Cases Case1.—Clinical History: A ten-year-old white girl was admitted to the Hospital of the University of Pennsylvania in Sept 1963 for evaluation of muscle weakness. She was the product of a normal gestation and delivery. The mother considered intrauterine activity comparable to that in her other pregnancies. The neonatal period was marked only by mild physiological jaundice. At two months of