Patients with acute leukaemia suffer from various haemorrhages, most frequently due to thrombocytopenia. We could not reach any information regarding the frequency of gastrointestinal bleeding in acute leukaemia and decided to search this complication in patients with acute and chronic leukaemias and myeloproliferative disorders, retrospectively.During a 6-year period, 291 patients with acute leukaemia, 52 patients with chronic leukaemia and 108 patients with myeloproliferative disorders had been followed. Thirty-two cases of overt gastrointestinal haemorrhage episodes (25 upper, 7 lower) were observed during the mentioned period.The frequency of bleeding episodes was 7.1% (32/451) in haematologic malignancies as a whole, 5.8% (17/291) for acute leukaemia, 1.9% (1/52) for chronic leukaemia and 13% (14/108) for myeloproliferative disorders. If the patients with myeloproliferative disorders in blastic phase were analysed separately, the ratio was 30% (6/20). Oesophagogastroduodenoscopy, which could be performed in 8 of 25 upper gastrointestinal haemorrhage episodes, revealed erosive gastritis in five patients and duodenal ulcers in three patients. Neutropenic enterocolitis was the underlying cause in all of the seven patients with lower gastrointestinal haemorhage. Five out of the seven patients had acute leukaemia. In 7 bleeding attacks, out of 32, the ultimate result was death. Generally, the haemorrhage was only a contributing cause of mortality. All of the mortality cases were patients with acute leukaemia.Especially, the patients with myeloproliferative disorders are prone to develop gastrointestinal haemorrhage. The manifestation is generally as upper gastrointestinal bleeding due to gastric erosions and duodenal ulcers. Lower gastrointestinal bleeding is frequently a problem of the patients with acute leukaemia. It is commonly a sign of neutropenic enterocolitis.