Patients who have low-risk clinical features and negative cardiac troponin levels may be suitable for early discharge after a brief period of observation in the emergency department (ED). Little is known about the prevalence and severity of coronary artery disease in such patients, although this has implications for follow-up. Subjects included 570 patients who were at < or =7% risk of acute myocardial infarction (AMI), remained clinically stable (defined as the absence of new ischemic changes on their electrocardiograph, signs or symptoms of heart failure, the development of a cardiac arrhythmia or hypotension requiring either inotropes or volume repletion) and had cardiac troponin I (cTnI) levels <0.2 microgl(-1) during the initial 12 hours of hospitalization. Clinical features were documented and those undergoing stress tests and/or coronary angiograms had these graded by 2 independent observers. Overall, 190 (33.3%) of this population, who might be considered suitable for early discharge, had objective evidence of coronary artery disease. Patients with chest pain who are at low risk of AMI, remain clinically stable and have negative cTnI over the initial 12 hours of observation are a heterogeneous population, some of who have threatening coronary disease. This does not preclude early discharge from the ED but emphasizes the need for careful assessment and follow-up.