We carried out a survey on platelet transfusions performed in nine general hospitals. We evaluated 303 adults who received a total of 24455 units over 1864 platelet transfusions. The underlying diseases were hematologic disorders with chemotherapy (59.7%), hematologic disorders without chemotherapy (15.5%), hematopoietic stem cell transplantation (18.5%), and others (2.0%). The patient platelet count before transfusion (platelet trigger value) was measured in only 77.1%. The platelet trigger value differed greatly between the hospitals, with an average of 2.2 x 10(4)/microl, a minimum of 1.3 x 10(4)/microl, and maximum of 3.2 x 10(4)/microl. Only 55.3% of the platelet transfusions carried out complied with the Platelet Transfusion Guideline published by the Ministry of Health, Labour and Welfare. The hospitals surveyed could be divided into those who gave mainly around 10 units and those who gave over 10 units. The total dose of platelets transfused was more in the hospitals that used mainly 15 or more unit-PCs than in the hospitals that used mainly 10 unit-PCs. These results indicate that platelet transfusion may be greatly reduced by complying with the 2 x 10(4)/microl of platelet transfusion threshold and by selecting less than 10 units of PC per transfusion.