A new type of amyloidosis, predominantly osteoarticular, has recently been recognized in uremic patients on hemodialysis, beta 2-microglobulin being the major constituent protein. Nowadays, it is not clear whether the amyloid deposition is limited to osteoarticular structures or whether it has a systemic character. In order to investigate the extension of dialysis amyloidosis, we studied 26 patients receiving hemodialysis treatment (mean time 12.2 years) for chronic renal failure due to nonamyloid nephropathy and who were affected by symptomatic dialysis amyloidosis. Twenty-two patients developed a carpal tunnel syndrome, and amyloid arthropathy was present in 21. Subcutaneous abdominal fat aspiration, rectal and skin biopsy, and two-dimensional echocardiography were performed in most of the patients, searching for the visceral involvement. Surgical pieces (one stomach and two colon) and three necropsies of symptomatic patients were included in the systemic investigation. Also, we studied five necropsies of patients without articular symptoms. Histological confirmation of amyloid visceral involvement was demonstrated in 15 (58%) of the 26 patients studied. When positive two-dimensional echocardiograms were included, the percentage increased to 81%. No differences in the rate of visceral involvement could be found between the two clinical groups (with and without carpal tunnel syndrome). Two-dimensional echocardiography represents the most useful tool to search for the visceral involvement of beta 2-microglobulin amyloidosis, followed by abdominal fat aspiration and rectal biopsy. Amyloid deposits were resistant to potassium permanganate treatment and reacted with antihuman beta 2-microglobulin (avidin-biotin-peroxidase method).