We present a 53-year-old man with rapidly progressive glomerulonephritis and Henoch-Schönlein purpura which developed during the course of treatment for polycythemia vera. An initial renal biopsy specimen showed mesangial proliferative glomerulonephritis. The patient was admitted to the hospital with cutaneous purpura and progressive renal failure after having received 700 mg of ranimustine over a 29 month period as therapy for the polycythemia vera. A second renal biopsy specimen revealed crescentic glomerulonephritis with deposition of immunofluorescent IgA. These data suggest that Henoch-Schönlein purpura nephritis may occur in response to ranimustine therapy.