The ready availability of platelet concentrates has undoubtedly made a major contribution to the supportive management of thrombocytopenic bleeding in patients with haematological malignancies. The optimal use of prophylactic platelet transfusions for the prevention of haemorrhage in patients with bone marrow failure remains controversial. Two RCTs of prophylactic platelet transfusions have recently been completed in adults with thrombocytopenia due to haematological malignancies or their treatment. Both found a no-prophylaxis approach led to higher rates of World Health Organization (WHO) grade 2?4 bleeding overall. Other patient groups who are major users of platelet transfusions are cardiac and other types of major surgery, critical care, major obstetric haemorrhage, trauma and paediatrics/neonates.