To review the normal coagulation process and the mechanisms that lead to abnormal clotting.Primary and tertiary literature and the authors' clinical experience.The process of coagulation is complex and can be easily misunderstood. It is important to be familiar with normal coagulation before one can comprehend the coagulopathies associated with malignancies.A thorough understanding of the coagulation process is a critical prerequisite to caring for patients with clotting disorders. Once the normal clotting process is understood, the abnormal becomes easier to recognize and the cancer-associated dysfunctions more readily identified.