Since the work of Putti (1929) the subject of preluxation or dysplasia of the hip which is the forerunner of true dislocation has been widely covered in numerous papers published during the second quarter of this century. The recent monograph of Hart (1952) contains a comprehensive summary of our present knowledge of this problem. There is but One feature which seems to have escaped notice-namely, the condition of the opposite hip in cases of unilateral dysplasia. While examining infants with signs of unilateral preluxation, I was impressed by the persistent abduction attitude assumed by the opposite hip. The contrast with the adducted, dysplastic hip was striking. On closer examination a more or less pronounced abductioncontracture was evident. It is the purpose of this paper to consider a series of fifty-one infants all presenting this singular association of a one-sided congenital dysplasia of the hip with an abduction-contracture of the opposite joint ; and, further, to suggest an explanatidn for the pathogenesis of unilateral dysplasia.