Echocardiography and doppler-echocardiography were used in the study of 14 patients with non-Hodgkin's lymphomas. The following manifestations of myocardial toxic effect of the tumor were found: derangements of elastic properties of the left ventricle and alterations of diastolic blood flow. Parameters of diastolic left ventricular function were compared in patients with various severity of tumor intoxication determined by levels of lactate dehydrogenase (LDH) and integral index of intoxication. Pronounced derangements of early and late filling flows took place in patients with high LDH levels. During chemotherapy alterations of diastolic blood flow became more profound apparently due to cardiac toxicity of antitumor agents.