Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Warkentin has served as consultant and/or has received honoraria for speaking on behalf of companies that manufacture LMWH (Pfizer Canada, Inc; Sanofi), heparin-coated grafts (W. L. Gore & Associates Inc), heparin-like molecules (Paringenix Inc), and non-heparin anticoagulants for management of HIT (Canyon Pharmaceuticals, GlaxoSmithKline). His institution has received funding from GlaxoSmithKline and Instrumentation Laboratories, as well as from the Heart and Stroke Foundation of Ontario for research related to HIT. Dr Warkentin has also received royalties from Informa for the book, Heparin-Induced Thrombocytopenia. He receives compensation for medicolegal consultation and testimony regarding thrombocytopenic disorders including HIT. Ms Sheppard is employed through grants received from the Heart and Stroke Foundation of Ontario for research pertaining to HIT. Dr Ernest has served as a consultant to and received grant monies from Hospira, Inc, a company that manufactures heparin. Dr Vlahakis is employed by Genentech, a company that manufactures thrombolytic agents (alteplase, tenecteplase). Dr Crowther has sat on advisory boards for Leo Pharma Inc; Pfizer Inc; Bayer; Boehringer-Ingelheim GmbH; Alexion Pharmaceuticals, Inc; CSL Behring; and Artisan Pharma, Inc. Dr Crowther has prepared educational materials for Pfizer Inc; Octapharma Plasma, Inc; and CSL Behring. Dr Crowther has provided expert testimony for Bayer and for Merck & Co. Dr Crowther holds a Career Investigator award from the Heart and Stroke Foundation of Ontario, and is the Leo Pharma Chair in Thromboembolism Research at McMaster University. His institution has received funding for research projects from Boehringer-Ingelheim, Octapharma Plasma, Inc; Pfizer Inc; and Leo Pharma Inc. Dr Crowther has received funding for presentations from Leo Pharma Inc and CSL Behring. Ms Heels-Ansdell and Drs Marshall, McIntyre, Rocha, Mehta, Davies, Bersten, Crozier, Hall, Wood, Poirier, and Cook have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.