A 10-year retrospective study of 36 patients is presented; the patients comprised 27 with renal micropolyarteritis nodosa (microPAN) and nine with Wegener's granulomatosis. At presentation, 29 patients had significant renal impairment (creatinine greater than 150 mumol/l), with 18 requiring dialysis at some time during their illness. Eighteen patients showed rapid recovery of renal function, a further two with apparently chronic renal failure recovered renal function after 4 months dialysis and continued immunosuppression. Seven patients required chronic dialysis. No benefit was shown for any particular immunosuppressive regime, with three patients recovering renal function (two initially on dialysis) without any immunosuppression. Prognosis was better than in previous published series, especially considering the elderly population (mean 52.9 years), with an 80% 1-year and a 64% 5-year survival.