Among 3,242 coronary angiograms performed from November 1972 through October 1975 at the Massachusetts General Hospital, 175 patients had normal coronary arteries or luminal narrowings of less than 30 per cent. All patients were studied for chest pain, and none had experienced prior myocardial infarction. Subsequent information was available in 159 patients over a mean follow-up period of 42.7 months. There were no deaths, and only one myocardial infarction occurred during this period. However, among the patients followed, continued chest pain with episodes occurring at least once monthly was present in 54 per cent. In addition, 17 per cent of all patients required subsequent hospitalization and 44 per cent continued to receive antianginal medication. Nearly half of the group (46 per cent) suffered some limitation of activity, and 22 per cent stated that they had either changed jobs or stopped work because of chest pain. Continuing chest pain was significantly more common in women and in patients who had experienced chest pain for more than one year before angiography. However, typicality of chest pain for angina or the occurrence of electrocardiographic changes of ischemia prior to angiography did not predict continued chest pain during the follow-up period. Thus, although mortality and morbidity are low in this group of patients, the syndrome of chest pain with angiographically insignificant coronary artery obstruction has an important impact on the lives of a majority of those affected.