The aim of prophylactic platelet transfusions in haemato-oncologic patients with thrombocytopenia is to prevent bleeding. Currently, a platelet transfusion trigger of 10 x 10(9) L(- 1) is considered to be safe. Transfusion compliance with this trigger can save costs. To investigate the compliance with this trigger of 10 x 10(9) L(- 1), we have evaluated 1447 platelet transfusions given during a period of 1 year to haematological patients. In half of the transfusions, there had been compliance with the trigger of 10 x 10(9) L(- 1). About three-quarters of all platelet transfusions were given at platelet counts < or =20 x 10(9) L(- 1). Transfusions at levels >20 x 10(9) L(- 1) were usually performed because of bleeding, scheduled interventions or concurrent anticoagulant therapy. We conclude that compliance with the prophylactic platelet transfusion trigger of 10 x 10(9) L(- 1) was about 50%; however, deviation from the trigger was partly explained by risk factors that justify a higher transfusion trigger.