Understanding the clinical appropriateness of a procedure's use may be critical in explaining geographic variations in its use. Little is known, however, about whether data on appropriateness can be obtained from a medical record. A national panel of physicians formulated a list of 300 mutually exclusive, detailed clinical indications for performing coronary angiography. Using this list, we compared the reasons physicians perform coronary angiography as revealed in medical records with those given in interviews with the physicians who actually did the procedure. Thirty-five of 47 eligible billing entities (74%) from two Los Angeles Professional Standards Review Organization areas participated. These physicians practiced in 14 hospitals and accounted for 81% of all angiographies performed on Medicare patients in the two areas. Sixty-six records (approximately two per physician) were reviewed; physician interviews were conducted by two trained data collectors who were blinded to each other's results. Ninety-one percent agreement was reached on the specific indication for performing coronary angiography when information from the record review and interview was compared. We conclude that medical records yield valid information on why coronary angiography is performed and that they are a suitable source to use in judging the appropriateness of that use.