Ten patients with rapidly progressive glomerulonephritis and acute renal failure were treated with extracorporeal immunoadsorption, prednisolone, and cyclophosphamide. Three patients had systemic lupus erythematosus, five had microscopic polyarteritis and two had Wegener's granulomatosis. All ten patients were dialysis-dependent prior to immunoadsorption. Nine of ten patients rapidly regained renal function and seven continue to have independent renal function between 9 and 30 months after immunoadsorption. Three patients at presentation were not dialysis dependent. Despite treatment with methylprednisolone, cyclophosphamide, and oral prednisolone, renal function continued to deteriorate and they required dialysis. Immunoadsorption was then started without alteration in baseline immunosuppression. Within a mean of 4.6 days, range 3-7 days, renal function improved and the patients no longer required dialysis. Antineutrophil cytoplasmic antibodies and double-stranded DNA antibodies were rapidly removed by immunoadsorption. Only one patient with systemic lupus erythematosus and two with microscopic polyarteritis had significant resynthesis of antibody at 1 month post-immunoadsorption. Renal biopsy before and after immunoadsorption and immunosuppressive therapy showed resolution of glomerular crescents and no evidence of active disease. Immunoadsorption coupled with prednisolone and cyclophosphamide may be of value in the treatment of rapidly progressive glomerulonephritis.