In 29 patients with clinical diagnosis of rheumatic valvular disease the quantitative values of active rosettes and the specific sensitization to human heart myosin were examined. The specific sensitization to human heart myosin was examined by two methods concurrently: method of inhibiting leucocyte migration in agarose and method for direct specific lymphocytolysis with myosin. The results were compared with those of 44 clinically healthy controls. In the patients with rheumatic valvular disease (RVD) the values of the active rosettes are significantly lower (p less than 0.01) than in the healthy controls. With the method of direct specific lymphocytolysis with myosin statistically significant sensibilization of the lymphocytes to myosin was found in the patients with RVD (p less than 0.001). In 5 patients examined before and after operation it was established that 2-4 weeks after a successful correction of the hemodynamics the specific sensibilization of the lymphocytes to myosin was no more present.