The quick and accurate diagnosis of acute coronary heart disease in the emergency department constitutes a first line medical challenge. About 5% of patients attending to the emergency department present chest pain or symptoms suggesting myocardial ischemia. A prompt diagnosis contributes to patient survival while an incorrect one can be associated to an increased risk of unfavorable outcome. On the other hand, unnecessary admissions into high technology hospital areas determine important expenses unacceptable from a cost-benefit point of view. In the present paper, the usefulness of different diagnostic tools used in emergency department (case history, electrocardiogram, nuclear perfusion imaging, echocardiography, exercise test) is reviewed, their advantages and limitations reviewed, with special emphasis on the importance of having an electrocardiogram as soon as possible, and based on the electrocardiographic findings the most appropiate management is discussed.