21 patients requiring bilateral total hip arthroplasty received two different hip prostheses, one with a distally tapered stem and the other with a distally cylindrical stem to determine the effect of the distal design on bone remodelling. Patients were randomized as to which leg received the different prostheses. 7 years after surgery, all patients displayed good clinical and radiographic outcomes. Cancellous condensation was found in Gruen's zones 2 and 6 around the cylindrical stem and between Gruen's zones 2 and 3, and zones 5 and 6 around the tapered stem. Bone mineral density around Gruen's zones 2 and 6 was significantly lower around the tapered stem than the cylindrical stem, indicating the tapered stems may experience more distal loading than the cylindrical stems.