Preoperative coagulation profile screening is routinely performed in otolaryngology before tonsillectomy and adenoidectomy surgery in the United States. Recently there has been controversy as to whether this routine testing is necessary. To evaluate the need for this testing, we reviewed a series of patients with particular attention to abnormal coagulation profiles. Of 91 consecutive patients undergoing tonsillectomy, adenoidectomy, or both, four had abnormal preoperative coagulation profiles. Of these patients, one had von Willebrand disease, one had hypofibrinoginemia, and two had a transient acquired lupus-like anticoagulant. The latter condition, which causes a temporary prolongation of the activated partial thromboplastin time, is discussed in detail along with a review of the pertinent literature. We conclude that coagulopathies occur frequently enough to justify preoperative screening even in the absence of a positive history