Amyloid-containing tissues were sampled from 19 capsules and 10 cartilages from hip, knee and sternoclavicular joints of 16 elderly patients. Heart ventricles from 3 of these patients were also studied. Histochemistry and immunofluorescence were performed and amyloid fibrils extracted from one hip capsule. The results indicate that 9 of 13 hip capsules contained prealbumin-like amyloid fibril protein ASc1, a finding characteristic of senile systemic amyloidosis. The amyloid of 16 out of 17 other joint structures showed no reaction with anti-ASc1 or antisera to 3 other systemic forms of amyloid, indicating that they represent localized forms of amyloid.