An infant with clinical features of Potter and Turner syndromes at birth was found to have a translocation of a portion of the long arm of a Y chromosome to a 21 chromosome, and only one X chromosome. The infant had bilateral dysplastic kidneys and hypoplastic lungs and suffered spontaneous rupture of the heart and pneumothoraces. Except for gonads with persistent sex cords and a solitary degenerating follicle, the genital organs were female. The sexual differentiation is compatible with the theory that the short arm of the Y chromosome is mainly responsible for male differentiation but implies that the long arm is not without effect on gonadal development. The occurrence of severe renal abnormalities in an infant with a sex chromosome abnormality may be more than coincidental.