Preoperative coagulation studies are commonly employed in order to try to identify the 2-4% of all patients undergoing tonsillectomy/adenoidectomy surgery who experience hemorrhagic complications. In an atmosphere of increasing cost consciousness, evaluation of the efficacy of screening tests is warranted. The records of 994 out of 1050 patients consecutively scheduled for tonsillectomy, adenoidectomy or T&A over a 2.5-year period were retrospectively reviewed in order to determine the usefulness of partial thromboplastin (PTT) and prothrombin time (PT) screening in predicting surgical and postsurgical bleeding. For patients with no history or clinical signs indicating possible bleeding disorder, preoperative PT and PTT failed to predict bleeding as an outcome. Also no patients were identified in this series to have previously undiagnosed coagulopathies on the basis of screening PT/PTT. The purpose of any screening test is to identify disease early enough for therapeutic intervention to be effective. Although preoperative PT/PTT will occasionally identify an unsuspected von Willebrand's or other coagulopathy, the prevalence of bleeding disorders in patients with negative history and examination is low enough that PT/PTT has essentially a zero predictive value for surgical bleeding. Screening PT/PTT should therefore be reserved for patients with known or suspected coagulopathies.