Introduction. Myocarditis is one of the most urgent and in many respects unresolved problems in cardiology. The situation is further aggravated by the ever increasing incidence of the of disease. The lack of knowledge about myocarditis etiology and pathogenesis creates a number of difficulties for the choice of the adequate treatment strategies. Aim. The objective of the present study was to evaluate the effectiveness of quantum photohemotherapy (PHT) with the use of a blue light in the combined treatment of infectious-allergic myocarditis (IAM). Material and methods. We examined a total of 28 patients including 12 women and 16 men at the age from 16 to 45 years suffering from IAM. The diagnosis of IAM was confirmed clinically, biochemically, and functionally with the application of the blood tests, chest X-ray examination, echo- and electro-cardiography. We used the classification of N.R. Paleev and M.A. Gurevich for myocarditis diagnostics. The diagnosis of ischemic heart disease was excluded according to the WHO criteria. The degree of heart failure in the patients was assessed based on the NYHA classification criteria. All the patients were given therapy with nonsteroidal anti-inflammatory drugs, metabolic drugs, anti-arrhythmics, diuretics, and angiotensin converting enzyme inhibitors. In addition, the generally accepted methods for the characteristic of blood rheological properties were employed. Moreover, the universally recognized rehabilitative and therapeutic measures were supplemented by blue light PHT using an AFS-Solaris light-emitting diode for intravascular irradiation of blood through the disposable light guides. Results. The study has demonstrated that IAM was accompanied by a number of hemorheological disorders that collectively make up a component of pathogenesis of the condition in question. The application of blue light PHT for the combined treatment of the patients with IAM led to the improvement in their rheological status and peripheral blood characteristics. Conclusion. Various hemorheological disorders were diagnosed in the patients suffering from infectious-allergic myocarditis. The main effect of blood viscosity reduction documented in the patients with IAM under the influence of blue light PHT was attributable to the reduction in hematocrit decreasing and suppression of the erythrocytes aggregation activity.