Aim. The aim of this work was to study the formation of diastolic and systolic heart failure in early phase of doxorubicin cardiomyopathy. Materials and methods. The cardiac contractile function in 30 Wistar rats has been studied through 4 and 8 weeks after the start of the introduction of doxorubicin (2 mg/kg weekly). The echocardiography and left ventricular (LV) catheterization have been used for pressure measurement and calculation of indicators of myocardial contractility and relaxability. Results. In the study of 15 animals received 4 injections of doxorubicin, the majority of animals (73%) had normal ejection fraction, while 27% animals had noticeably reduced fraction. In rats with normal ejection fraction, the LV diastolic pressure was increased while relaxation constant decreased, which is typical for diastolic dysfunction. These changes were maintained at the same level in some animals (43%) through 8 weeks. Incidence of systolic dysfunction increased from 27% after 4 weeks up to 57% after 8 weeks. It was characterized by the predominant decrease in contractility indices, as well as the elongation of systolic phase and reduced heart rate. Reduced ejection fraction in all experiments well correlated with decreased contractility index (r=0.68), and relaxation constant (r=0.61). Conclusion. Diastolic dysfunction is the first phase of the development of doxorubicin cardiomyopathy and chronic heart failure.