Doppler ultrasound examination confirmed the diagnosis of acute venous thrombosis in only 194 (37%) of 527 patients. Of the remaining 333 patients, 245 (74%) had some other evident cause of the limb complaints. The postphlebitic stasis syndrome; symptomatic varicose veins; congestive heart failure; leg trauma; venous or lymphatic obstruction by malignancy; cellulitis or lymphangitis; arthritis; and pregnancy were etiologic factors in these patients. The proved inaccuracy of the bedside diagnosis of leg vein thrombosis stresses the need for accurate objective verification of venous disease before committing the patient to a full course of anticoagulant therapy. For most clinicians, a contrast phlebogram is the most available and reliable diagnostic procedure.