Heparin-induced thrombocytopenia (HIT) is an immune-mediated condition characterized by thrombocytopenia with possible arterial and/or venous thrombosis. The overall incidence of HIT is low but ranges from 0.1% to 5%. The incidence can be as high as 3% in patients undergoing cardiac surgery. The use of unfractionated heparin (UFH) is ubiquitous in patients who undergo cardiac procedures and carries a 10-fold higher incidence of HIT over low molecular weight heparin. Patients undergoing cardiac surgery thus form a unique group that warrants specific attention to this clinicopathologic entity considering the relatively high incidence and associated morbidity and mortality with a delay in diagnosis. In this article, we will discuss 5 clinical aspects pertinent to the diagnosis and management of HIT in cardiac surgery patients and review the current literature.