The first half will provide an overview of basic platelet antibodies (allo, auto and drug induced antibodies), the testing methods used to detect and identify various types of platelet antibodies, as well as provide some insight as to what sorts of technical problems can be seen when performing platelet testing. The second half will answer a number of questions with regards to the clinical side of platelet transfusions and refractoriness. What leads to refractoriness? Can alloimmunization be prevented (e.g. the TRAP trial data)? What products are the best for patients with antibodies that may or may not have refractory issues? Does ABO type play a role in patients with antibodies? Lecture and case study will be the instruction method.