Despite treatment with intensive immunosuppressive drug regimens, the prognosis of patients suffering from severe progressive autoimmune diseases like systemic lupus erythematosus (SLE), nephrotic syndrome (NS), and Behqet's disease is poor. Side effects (infections and malignant tumors) often occur. In the present trial, 35 patients suffering from autoimmune diseases (SLE, n = 21; NS, n = 10; and Behqet's disease, n = 4) were treated for 3.7 f 2.0 years with 2.5 0.6 mg cyclosporine/kg body weightlday in addition to corticosteroids alone or in combination with azathioprine and/or cyclophosphamide. In active stages of the diseases with extremely high concentrations of anti-ds-DNA-antibodies, antinuclear antibodies, circulating immunocomplexes, and reduced complement concentrations, therapeutic plasma exchange (TPE) has been applied. Compared with previous treatment modalities, significantly (p < 0.05) more effective and rapid reductions of the antibodies were reached. Clinical disorders improved within 1-6 weeks. All patients reported increased performance and a better quality of life. After 1-12 months, the previously required doses of immunosuppressive drugs and the frequency of TPE could be reduced by 40-100%. After 13.4 * 11.8 months in 17 of 35