The level of 20x10(9)/L for prophylactic platelet transfusion has rightly been challenged over the last few years, with some units recommending a level as low as 5x10(9)/L. The higher levels are usually based on retrospective data from the 1950s. We examined the more recent data and came to the conclusion that a threshold of 10x10(9)/L is safe in the stable patient; higher levels are recommended for specific clinical circumstances. This threshold will reduce donor exposure, costs and possibly donor alloimmunization. The dearth of prospective controlled clinical trials in the literature also presents an opportunity for both in-house and national audit.