Acute Myocardial Infarction (AMI) requires rapid and accurate diagnosis specially now that new treatment options with thrombolytic agents are available. The laboratory tests help to make this diagnosis at an early stage. Troponin I is a specific cardiac marker elevated only in patients suffering from AMI. Troponin T rises 2-4 hours after the onset of myocardial necrosis and remains elevated upto 14 days. It may also be used to monitor patients with non-ischemic causes of cardiac injury. High levels are also seen in unstable angina. Measurement of both troponins has a sensitivity & specificity of nearly 90% and persistent elevation 12 hours after the onset of chest pain has 100% sensitivity in diagnosing AMI. CPKMB fraction is predominantly found in cardiac muscle and serial measurements during AMI at 3-4 hour intervals over 12-16 hour period is a useful test.