Thrombosis of the hepatic veins (Budd-Chiari syndrome) is a life-threatening thrombotic complication which can occur in patients with paroxysmal nocturnal haemoglobinuria (PNH). Despite aggressive medical and surgical therapy, mortality from Budd-Chiari syndrome remains high. We report a boy with PNH who developed Budd-Chiari syndrome and underwent syngeneic bone marrow transplantation (BMT). Now, 3 years following BMT, he has had dramatic clinical and radiographic evidence of resolution of the thrombosis. We suggest that BMT for PNH can successfully correct life-threatening thrombosis in patients with PNH.