Background: Myocardial infarction, or heart attack, occurs when there is prolonged total occlusion of coronary arterial blood flow. The larger the necrotic area is, the more serious the damage. Aim: of the study was to assess patients' knowledge and perception regarding myocardial infarction. Subject and Methods:   A descriptive research design was used to conduct this study. A convenient sample of 90 patients who have myocardial infarction through 6 months and attended intensive care unit and outpatient clinic in Specialized Hospital and coronary care unit and outpatient clinic in El- Azhar Hospital in Damietta. Tools were used to collect data: includes Sociodemographic characteristics, patient personal medical history, patients' knowledge questionnaire and patients' perception questionnaire. Result: The results revealed that the most of the studied patient had unsatisfactory knowledge about nature and causes of, myocardial infarction symptoms, risk factors of myocardial infarction (71.1%, 93.3%, 54.4% respectively).  Also more than three quarter (81.1%) of the studied patients had highly positive perception regarding myocardial infarction. While, there was highly statistical significant relation between total patients' perception and knowledge of myocardial infarction.  Conclusion:  the most of studied patients had highly positive perception about myocardial infarction and there no statistical significant relation between age, level of education and patient's perception