Between 1981 and 1984, 72 patients (22-75 years) were included in a prospective study for treatment of Polyarteritis Nodosa (PN) which associated therapeutic plasma exchanges (TPE), corticosteroids (CS) 1 mg/kg/day, and a randomized trial of cyclophosphamide (CP) 2 mg/kg/day. We observed the incidence and analysed side effects (SE) occurring during TPE considering the technology of plasma removal. Full data were available for 63 patients. Seven hundred and eighteen TPE were performed. Centrifugation was used in 594 PE (82.7 per cent) with intermittent flow centrifugation (IFC) 320 times (44.5 per cent) and continuous flow centrifugation (CFC) 274 times (38.2 per cent). Filtration (F) was used in 124 sessions (17.3 per cent). Replacement fluid was 4 per cent albumin in 650 TPE and fresh frozen plasma (FFP) in 89 TPE. A total of two hundred and eleven SE were reported in 53 patients (84.1 per cent) during 173 TPE (24.1 per cent). Forty-six TPE were temporarily stopped because of SE (6.4 per cent). The mean volumes of removed plasma (ml/kg/TPE) were: 60.7 +/- 8.7 ml/kg when CFC was used 54.5 +/- 20 ml/kg with F and 52.5 +/- 9.6 ml/kg with IFC (n.s.) Main SE were: technical difficulties in 80 TPE, moderate or severe hypotension in 47, allergy to replacement fluid in 39. Hepatitis B antigen appeared in one patient. No death occurred during TPE and SE were usually minor and transient.(ABSTRACT TRUNCATED AT 250 WORDS)