Background: Routine use of ACE inhibitors (ACE-I) as secondary preventive therapy for all patients with coronary artery disease (CAD) is challenged by the PEACE trial. Currently it is unclear to what extent ACE-I should be used in CAD populations. Purpose: To analyze the prevalence of left ventricular systolic dysfunction, diabetes, myocardial infarction and hypertension in an unselected and consecutive population of patients with documented CAD and evaluate the potential need for ACE-I treatment in a real-life scenario. Methods: We searched a database containing all invasive cardiac investigations in three hospitals in Copenhagen from July 1, 2000 to June 30, 2003. Patients with no angiographic sign of CAD were excluded. Results: Among 7,345 patients, 4,180 had stable CAD and 3,165 had acute coronary syndrome (ACS). Among the stable CAD patients 78% had at least one of the following indications for treatment with an ACE-I: left ventricular ejection fraction <0.45 (20%), hypertension (39%), diabetes (19%), systolic blood pressure >159 mm Hg (21%), and/or myocardial infarction (42%). Among ACS patients, 90% had an indication for ACE-I treatment. Conclusion: Depending on the definitions, at least 78% of the patients with stable CAD and 90% with ACS have an accepted indication for treatment with an ACE-I.