One hundred and forty patients with classic or definite rheumatoid polyarthritis were treated with N2 mercapto-propionly-glycine: thiopronine (Acadione) at an average dose of 1 g per day over a mean duration of 11.7 months + 10.7 months. The retrospective study of these cases, followed between 1980 and 1988 by the same medical team, permits to evaluate the long-term tolerance of the product. Adverse reaction, always subsiding were observed in 55 p. cent of the patients, requiring discontinuation of the treatment in 40 p. cent of the cases. These side effects occur in 3/4 of the cases, during the first 6 months of the treatment. The intolerance mainly affect skin and mucosae: 46 cases (32.8 p. cent) resulting in 32 instances (22.8 p. cent) discontinuation of the treatment because of stomatitis, pruritus, various types of erythema, pemphigus (1 case). Fourteen patients presented a renal failure (10 p. cent) requiring in 8 instances (5.7 p. cent) discontinuation of the thiopronine because of nephrotic syndrome (3 case) and proteinuria (5 cases). Haematological disorders were observed in 13 instances (9.2 p. cent), justifying, in 10 instances (7.1 p. cent) discontinuation of the treatment because of thrombopenia or leucothrombopenia. The other side effects observed are the following: digestive disorders 15 cases (10.7 p. cent) requiring discontinuation of the treatment in 3 instances (2.1 p. cent), agueusia in 6 instances (4.2 p. cent) requiring discontinuation of the treatment in one case; miscellaneous disorders 13.5 p. cent for which the responsibility of thiopronine is not precisely established (especially hepatic cholostasis, muscle disorders), requiring discontinuation the the treatment in 1.4 p. cent of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)