In patients with chronic renal insufficiency (CRI) treated by programmed haemodialysis (HD) were detected, during the last years, amyloid stores at the level of carpal tunnel, of some joints, bones etc., finding which permitted to describe a new type of amyloid, the so-called "dialysis associated amyloid". The immunochemical structure of this amyloid is similar to that of the beta-2-microglobulin (beta-2m). Patients display various clinical manifestations. The variations of serum and urinary beta-2m were studied in 51 uraemic patients chronically dialyzed by means of dialyzers with cuprophan membrane, the average duration of the HD treatment being of 51.5 months. The pre- and postdialysis values of the beta-2-m were determined by Mancini radial immunodiffusion. A considerable increase--about 25 times--of serum beta-2-m was observed, which was more marked in anuric patients and those with a duration of more than 5 years of HD treatment. Among these, 15.7% show various articular manifestations (detected clinically and radiologically): a carpal tunnel syndrome (one patient required surgery) and arthropathies with various sites (scapulohumeral, knee). During a HD sitting with cuprophan membrane dialyzers, an increase of beta-Z-m was recorded, but it was statistically non-significant.(ABSTRACT TRUNCATED AT 250 WORDS)