We reviewed the records of treatment of eighteen infants with congenital dysplasia, subluxation, or dislocation of the hip who had problems with the involved hip following treatment with the Pavlik harness. The most common problem (seen in twelve patients with a dislocated hip) was failure to obtain reduction. This failure was attributed primarily to improper use of the harness by the physician. In some patients, three to five months elapsed before the physician recognized the lack of reduction. In nine patients, a Pavlik harness of poor quality and construction added to both the physician's and the patient's problems, and in six patients, poor patient compliance with the use of the harness was partially responsible for the failure. In three patients who were initially treated in the Pavlik harness, avascular necrosis of the hip subsequently developed, in two following open reduction and in one after closed reduction and cast application. The physician's indications for use and application of the harness must be appropriate. The child must be examined frequently out of the harness both clinically and roentgenographically. Failure to achieve reduction or adductor relaxation must be recognized promptly and dealt with immediately.