This chapter discusses haematological emergencies, including blood transfusion reactions, sickle-cell crisis, bleeding disorders, abnormal coagulation, circulating inhibitors of coagulation, abnormal platelets, anticoagulant therapy, bleeding with fibrinolytic therapy, bleeding in liver disease, bleeding in uraemia, massive transfusion/cardiopulmonary bypass, haemophilia and related disorders, combined thrombotic and haemorrhagic disorders, disseminated intravascular coagulation (DIC), thrombotic thrombocytopenic purpura (TTP) and haemolytic uraemic syndrome (HUS), microangiopathic haemolytic anaemia, heparin-associated thrombocytopenia, acute leukaemias, early complications of bone marrow transplantation (BMT), the febrile neutropenic patient, infections in the transplant patient, cytomegalovirus (CMV) infections in transplant patients, hyperviscosity syndrome, tumour lysis syndrome, hypercalcaemia of malignancy, superior vena cava obstruction, and massive mediastinal mass.