Six simultaneous bilateral total hip arthroplasties were performed with an ingrowth prosthesis in one hip and a conventional cemented prosthesis in the contralateral hip. Clinical and radiographic examinations of the patients were obtained for a maximum of three years for an early comparison of the two prostheses. Although no functional difference was established between the two arthroplasties, all patients preferred the cemented hip because of less pain and no limp. Range of motion and functional ability of the hips were identical in all evaluations. Pain was slightly higher in the hip incorporating the ingrowth prosthesis, and walking ability was better with the cemented hip. No radiolucency was evident around the cemented femoral component or around either acetabulum in any of the patients. Half of the patients encountered initial subsidence of the ingrowth prosthesis, which later stabilized and proved to be insignificant. Ectopic bone formed on the posterior femoral neck of all the ingrowth hips. Sclerotic lines were observed in four of these patients but showed no correlation to the physical ability of the patients. Therefore, the ingrowth or uncemented hip arthroplasty appears to be functionally equivalent to the cemented hip arthroplasty and more symptomatic.