The morphologic features of amyloidosis associated with long-term hemodialysis for chronic renal failure were studied in a series of 16 patients in all of whom immunohistochemical evidence of beta 2-microglobulin-related amyloidosis was obtained. Osteoarticular involvement was present in 15 cases, as demonstrated in synovial biopsies, articular fluid sediments, three surgically obtained femoral heads, and 1 autopsied case. Amyloid was found in synovial membrane, articular cartilage and capsule. Osseous lesions due to amyloid infiltration were found in 2 cases with spontaneous fracture of the femoral neck. Thirteen patients had also amyloid in tissues obtained from carpal tunnel. Systemic involvement was demonstrated in 8 patients by means of rectal biopsies, abdominal fat aspiration biopsies, surgical specimens and autopsy. Deposition in the muscular layer of the gastrointestinal tract was found in 3 cases. Nodular subendothelial deposits in vessels of multiple sites seem to be characteristic of this type of amyloidosis. Immunohistochemical reactions for beta 2-microglobulin and P component were strongly positive in amyloid deposits of all cases. According to our results, abdominal fat aspiration biopsy has little value for screening purposes, whereas the study of articular fluid sediment is highly sensitive as a diagnostic method in patients with articular effusions.