Platelet transfusion is an essential part of the treatment of cancer, hematological malignancies, marrow failure, and hematopoietic stem cell transplantation. Refractoriness to platelet transfusions is often multifactorial. It is caused by immune and non immune factors. This book inculeds introduction about Platelet transfusion, Platelet refractoriness, Human leukocyte antigen, HLA typing, HLA antibodies and Human platelet antigens. This book is useful for Medical student, Doctors, specialists of blood transfusions and physicians in cancer institutes.