The authors describe the case-report of a 72-year-old female patient with acute failure of a solitary kidney with complete functional breakdown which developed within several days and was due to rapidly progressive glomerulonephritis (RPGN) with concurrent positivity of antineutrophil cytoplasmatic autoantibodies (ANCA) and anti-glomerular basement antibodies (AGBMA). Intensive combined immunosuppressive therapy with methyl prednisolone, cyclophosphamide and azathioprine and concurrent plasmaphereses led to negativity of both types of antibodies but were not able to restore sufficient renal function and regular dialysis treatment to be started. Subsequently AGBMA remained negative, while ANCA became again positive. Despite this partial restoration of renal function was manifested by an increased diuresis and the frequency of dialyses could be reduced. The case-report has several remarkable features. An uncommon RPGN of the antirenal type is involved, moreover in a solitary kidney with concurrent C-ANCA positivity. The concurrent presence of ANCA and AGBMA autoantibodies in RPGN has been described in the literature only in several tens of cases. So far it was not described in our country. Based on their experience the authors conclude: 1. a solitary kidney cannot be considered in case of suspected RPGN as a strict contraindicatio of renal biopsy, 2. RPGN with concurrent positivity of ANCA and AGBMA is indicated for long-term immunosuppressive therapy on account of a more favourable prognosis than simple antirenal RPGN, and also with regard to a possible suspected systematic vasculitis.(ABSTRACT TRUNCATED AT 250 WORDS)