ABSTRACT: Until recently, only bovine-derived thrombin was available for use as a stand-alone topical hemostat or as a component of other hemostatic devices. Concerns over a number of case reports of immune-mediated coagulopathies associated with the use of bovine-derived thrombin resulted in a United States Food and Drug Administration warning letter being issued in 1996 and the later addition of a boxed warning ("Black Box Warning") to all bovine-derived thrombin products. Since 2007, both a human-pooled plasma thrombin product and a recombinant thrombin have entered the market.With the addition of these two products to the topical thrombin class, a unique situation has developed in which only a single member (bovine-derived thrombin) within the class carries the Food and Drug Administration's strongest cautionary language about possible adverse events related to an agent's use. Neither the human-pooled plasma thrombin nor the recombinant thrombin products have a boxed warning; although, the human-pooled plasma product does include a precaution/warning about infectious agent transmission - a warning common to products derived from human sources. This report will address this unique situation and the impact, clinical and non-clinical, that thrombin choice may have. Since alternatives are now available, institutions may need to revisit their formulary choice of thrombin preparation, taking into consideration the potential risks associated with bovine-derived products.