THE USE of anticoagulants has become accepted in the management of patients with thrombo-embolic disorders. Bleeding is widely recognized as a frequent complication in patients who have been made hypoprothrombinemic for therapeutic reasons. Nichols et al.1 state that in a group of 73 patients treated with anticoagulants, 25% developed mild to moderate hemorrhage. Because of the frequency of this complication, the management of the hypoprothrombinemic patient who is bleeding is often limited to a reevaluation of prothrombin times and drug dosage. In contrast, patients who are not receiving anticoagulants and who bleed spontaneously usually undergo a thorough diagnostic study. It must be kept in mind that a bleeding episode in an anticoagulated patient may provide a fortuitous unmasking of a hitherto unrecognized lesion. The literature fails to emphasize this point, which is illustrated by the following 3 cases. Report of Cases Case 1.— A 46-year-old Puerto Rican male