Following myocadial necrosis associated with myocardial infarction (MI), myoglobin is one of the first markers to rise above normal levels, increasing measurably above baseline within 2-4 hours post-infarct, peaking at 9-12 hours, and returning to baseline within 24-36 hours.1,2 In the absence of skeletal muscle trauma or other factors associated with a non-cardiac related increase in circulating myoglobin, myoglobin levels have been used as an early marker for MI.3,4 A number of reports suggest the measurement of myoglobin as a diagnostic aid in “ruling-out” myocardial infarction with negative predictive values of up to 100% reported at certain time periods after onset of symptoms.