Hyaline sclerosis of synovial capillaries and venules was found at autopsy in fifty-two of seventy-two patients who presented no symptoms or anatomical evidence of joint disease. The lesion was found in small and large joints of both the upper and lower extremities, but occurred most frequently in the acetabular fat pad and the peripatellar region. Although apparently a retrogressive phenomenon, the lesion occurred as early as four years of age. Gamma globulin was not present in the walls of affected vessels. It is suggested that the lesion may arise from circulatory alterations in synovial tissues subjected to articular compression. In five elderly individuals, there was, in addition, arterial occlusion associated with focal, apparently healed, infarcts of the acetabular synovial pad.