The terms 'platelet transfusion trigger' are used in the scientific literature to indicate a value of the platelet count above which prophylactic platelet transfusion is usually not indicated. Most clinicians share the currently prevalent consensus published in several guidelines that a platelet transfusion trigger of 10,000 platelets per microliter is safe in stable oncohematology recipients carefully monitored at both the clinical and laboratory levels, whereas higher values may be necessary in patients with high fever, infection, splenomegaly, rapid platelet count decrease, on drugs able to affect platelet function and survival, in cases undergoing invasive maneuvers and in some pediatric patients such as premature newborns. The safety of this policy is supported by the results obtained in several randomized clinical trials and prolonged observational studies. Lowering the platelet transfusion trigger from the traditional value set at 20,000 platelets per microliter to the currently recommended value of 10,000 per microliter further stresses the importance of high-quality, sufficient and prompt platelet availability and close cooperation between clinicians and blood transfusion specialists. Furthermore, it requires a clear understanding of the discriminatory power of current automated hematology counters at very low platelet counts. In the surgical setting, where randomized clinical trials on the most appropriate platelet transfusion trigger are largely missing, current guidelines propose to maintain higher platelet count values (50,000-100,000 per microliter) during surgery and in the early postoperative period.