Successful cementless total hip arthroplasty is dependent on initial stabilization at the bone-prosthesis interface. Other factors, such as the adaptability of the prosthetic design to fit specific bony geometries, affect clinical outcome. These design considerations have been incorporated into the Mallory-Head (Biomet Inc., Warsaw, IN) prosthetic system so that it allows for immediate rigid stabilization of both the acetabular and femoral component in an effort to optimize the potential for bone ingrowth. Fifty primary cementless total hip arthroplasties, all performed by or under the direction of a codesigner of the prosthetic system, are reviewed. The average age of the patients was 53 years; the follow-up range was 24 to 52 months. The predominant preoperative diagnosis was osteoarthritis (88%). Using the Harris hip score, a noted improvement was seen in the preoperative score of 37 to a postoperative score of 94. Ninety-seven percent of the patients reported no pain or discomfort. In the Engh fixation scale, all femoral components were rated as optimum with signs of bone ingrowth. Radiographic evaluation showed no subsidence or shift of the femoral components. Five patients were noted to have acetabular migration of 4 mm to 6 mm. However, all were asymptomatic and fully functional in daily living activities. The early results of this cementless design compare favorably with those of similar series of cementless total hip arthroplasties.