In this single-center study, we retrospectively analyzed incidence and risk factors for hepatic veno-occlusive disease (VOD) in 249 consecutive patients who underwent allogeneic hematopoietic stem cell transplantation between January 1990 and June 1995. Twenty-four of the 249 transplanted patients developed VOD. The probabilities of developing VOD were 17% among women and 7% in men (P =.01). In women treated with norethisterone, the incidence was 27% compared with 3% in women without this treatment (P =.007). One-year survival rates were 17% and 73% in patients with (n = 24) or without VOD (n = 225), respectively. The use of heparin prophylaxis (100 IE/kg/24 hours for 1 month) did not alter the incidence or 1-year mortality of VOD. In multivariate analysis, the following risk factors were significant: norethisterone treatment (P <.001), bilirubin >26 micromol/L before bone marrow transplantation (BMT) (P =.002), one HLA-antigen mismatch (P =.003), previous abdominal irradiation (P =.02), and conditioning with busulphan (P =.02). Our conclusion is that norethisterone treatment should not be used in patients undergoing BMT and heparin prophylaxis did not affect the incidence or mortality of VOD.