Two radiologists independently assessed 100 leg vein phlebograms for the presence or absence of deep venous thrombosis. In a subsequent questionnaire, 66 physicians were asked to state the level of agreement they would require to use conventional phlebography in their diagnostic decisions, and whether they would reduce their requirements if the phlebographic technique were made less painful and less expensive. The responses indicated physicians' requirements for reproducibility of a well-known routine diagnostic method may be unrealistic, and that physicians do not consider the inconvenience of an examination to the patient or its cost in setting their requirements for diagnostic precision.