To study the influence of type A behavior (TAB) on infarct size and short-term prognosis of patients with acute myocardial infarction (AMI). Methods: 90 AMI patients were divided into TAB group (46 cases) and non-TAB group (34 cases) according to the TAB questionnaire. The infarct size was determined by peak level of CK and CK-MB as well as a QRS scoring system. The incidence rates of cardiac events during 4 weeks were also analyzed. Results: The peak value of CK and CK-MB as well as QRS score in TAB group were significantly higher than corresponding measures in non-TAB group (p<0.05). Rates of malignant ventricular arrythmia, post-infarction angina, reinfarction, heart failure and mortality were markedly higher in TAB group than in non-TAB group (26% versus 5.9%; 32.6% versus 8.8%; 19.6% versus 0%; 23.9% versus 2.9%; 17.4% versus 0%). Conclusion: TAB constituted a potentially contributing factor to enlargement of infarct size, affecting unfavorably the prognosis of patients with first AMI. To study the influence of type A behavior (TAB) on infarct size and short-term prognosis of patients with acute myocardial infarction (AMI). Methods: 90 AMI patients were divided into TAB group (46 cases) and non-TAB group The infarct size was determined by peak level of CK and CK-MB as well as a QRS scoring system. The incidence rates of cardiac events during 4 weeks were also analyzed. Results: The peak value of CK Rates of malignant ventricular arrythmia, post-infarction angina, reinfarction, heart failure and mortality were markedly higher in TAB group than in non-TAB group (26% versus 5.9%; 32.6% versus 8.8%; 19.6% versus 0%; 23.9% versus 2.9%; 17.4% versus 0% of infarct size, affecting unfavorably the prognosis of patients with first AMI.