Thermography (TG) is used as a contact free method for investigation of the myocardium ischemic injury. In coronary bypass surgery without artificial blood circulation it is important to know how cessation of blood supply affects the myocardium. In experiments on working heart, TG allows monitoring temperature at the desired point of the epicardium. The aim was to investigate relations between myocardial ischemia and temperature and to prove that the ischemic tissue and border zones can be determined by TG. Experiments were performed on mongrel dogs. In the areas of induced ischemia, ventricular surface thermograms (T) and electrograms (EG) were recorded. The obtained data showed that temperatures in ischemic area and border zone of myocardium were different from those in healthy myocardium. A detailed analysis of T of ischemic area showed that between ischemic and healthy myocardium a border zone is formed which is very important for arrhythmia genesis. The border zone is several millimeters wide, and its temperature is 1C higher than in healthy myocardium. The curve of the dynamics of temperature measured at all points of the ischemic zone has been created. Correlation between myocardium temperatures and characteristics of EG of ischemic zones is shown. Conclusion. The data show that TG is an appropriate method for determination of ischemic area and border zone in ventricular myocardium. TG gives a possibility to evaluate functional status of myocardium in a contact free way and may be applied for determination of ischemic damage of myocardium during cardiosurgery.