The acute coronary syndrome (ACS) represents a diagnostic challenge: on the one hand patients need to be quickly identified to initiate treatment and on the other hand early exclusion of patients without ACS is important to relieve patient stress as well as overcrowded emergency departments. A growing number of biomarkers are becoming available to aid physicians with this task. This review gives an overview of the current research concerning early exclusion with an emphasis on the clinically most important biomarker: cardiac troponin.