A 28 year old man presented with haematuria and renal failure. Renal arteriography revealed bleeding into the pelvis of a solitary right kidney from a hilar artery. Multiple aneurysms were noted in the splenic artery. The spleen subsequently ruptured spontaneously and was removed at laparotomy together with the right kidney. Histological examination of the spleen and kidney revealed an acute necrotizing vasculitis involving medium-sized and smaller arteries confirming a diagnosis of polyarteritis nodosa. An area of infarction involved a subcapsular area of the spleen. Spontaneous splenic rupture is a rare but important complication of systemic vasculitides.