Ambulatory coronary arteriography was carried out in 604 patients, 143 women and 461 men, mean age 53 +/- 14 years. An absolutely stable clinical condition was the main criterion of selection for this investigation and the protocol consisted in day-hospital admission, absence of routine anticoagulation, small calibre (5 French = 1.7 mm diameter) catheters, mobilization 4 hours and discharge 6 hours after the end of the procedure. The percutaneous femoral approach was used in 95% of cases; 56% of patients presented significant single-or multi-vessel coronary artery disease: there were 7 cases of left main coronary artery narrowing; 31 patients required full hospital admission, mainly because of the severity of coronary lesions. Minor complications occurred in 2% of cases.