Common uses of the granulocyte-colony stimulating factors in the clinical practice raise the concern about side effects of these agents. We presented a case report about an acute myocardial infarction with non-ST segment elevation during filgrastim administration. A 73-year-old man had squamous cell carcinoma of larynx with lung metastasis treated with the chemotherapy. Second day after the filgrastim, patient had a chest discomfort. An ECG was performed and showed an ST segment depression and negative T waves on inferior derivations. A coronary angiography had showed a critical lesion in right coronary arteria. This is the first study thats revealed that G-CSF can cause acute myocardial infarction in cancer patients without history of cardiac disease. Patients with chest discomfort and pain who are on treatment with G-CSF or GM-CSF must alert the physicians for acute coronary events.