Background/aim: To evaluate pregnancy-associated plasma protein A (PAPP-A), ischemia-modified albumin (IMA), procalcitonin, and troponin I levels as diagnostic markers of acute coronary syndrome in patients admitted to the emergency department. Materials and methods: The serum PAPP-A, IMA, procalcitonin, and troponin I levels were measured in 100 patients with acute coronary syndrome admitted to the emergency department and 100 healthy control subjects. Results: Patients with acute coronary syndrome had significantly greater mean serum PAPP-A (patients, 10 ± 10 mIU/L; control subjects, 6 ± 10 mIU/L; P ≤ 0.001), procalcitonin (patients, 2 ± 10 μg/L; control subjects, 0.4 ± 2 μg/L; P ≤ 0.001), and troponin I levels (patients, 6 ± 8 μg/L; control subjects, 0.2 ± 0.3 μg/L; P ≤ 0.001) than control subjects. There was no difference in mean IMA levels between patients and control subjects. There were no significant correlations between PAPP-A levels and IMA, procalcitonin, or troponin I levels in patients with acute coronary syndrome. Conclusion: The PAPP-A, procalcitonin, and troponin I levels were increased in patients with acute coronary syndrome. Therefore, elevated PAPP-A and procalcitonin levels, in addition to troponin I levels, may be useful markers of myocardial injury on admission to the emergency department.