Minor differences in size between the two sides of the body are common and usually have no significance. However, severe disproportion is relatively rare and there are less than 130 cases reported in the literature. In 1953 Silver and co-workers1described a syndrome of congenital hemihypertrophy and elevated excretion of urinary gonadotropins in two children who failed to show any other evidence of apparent endocrine disturbance. The purpose of this paper is to present the third case of this syndrome in a 7-year-old boy. Report of Case A boy was first seen in the New Haven Hospital Pediatric Out-Patient Clinic at the age of 10 weeks because of a difference in size of his legs. He had been born at term following an entirely uneventful pregnancy and had been delivered by Caesarian section. Birth weight was 3100 gm. (6 lb. 12½ oz.). Because he was cyanotic at birth, he