The early and late roentgenograms of the first 100 consecutive Charnley low friction arthroplasties, performed at the Hospital for Special Surgery from October 1968 to October 1970 demonstrate interesting reactions of joint structure. Osteoporosis, early breakage of the wires and trochanteric bed covered by cement were the main factors preventing or delaying the healing of the osteotomy of the greater trochanter. Almost all hips showed a radiolucent line at the acetabular bone-cement junction and about half at the femoral junction. One-third of the hips had increased femoral cortical thickness. Four hips had sterile loosening of the femoral component with a varus shift. Though about one-third of the hips had some ectopic ossification, in only 3 hips was it severe enough to adversely affect the end result. The use of radiopaque cement seems advantageous over the radiolucent type. Arthrography has proven useful for the diagnosis of complications, particularly if subtraction technique is employed.