We previously reported substantial disagreement among expert physician panelists about the appropriateness of performing six medical and surgical procedures for a large number of theoretical indications. A recently completed community-based medical records study of about 4,500 patients who had one of three procedures--coronary angiography, upper gastrointestinal endoscopy, and carotid endarterectomy--shows that many of the theoretical indications are seldom or never used in practice. However, we find that there is also substantial disagreement (5, 25, or 32 per cent for angiography, endoscopy, or endarterectomy, respectively) about the appropriateness of indications used in actual cases if disagreement is defined by first discarding the two extreme of nine ratings, then looking for at least one rating near the bottom (1 to 3) and one near the top (7 to 9) of the 9-point scale. Patients should know that a substantial percentage of procedures are performed for indications about which expert physicians disagree.