Recently, the contribution of the immune system in the development and progression of arteriosclerosis has been suggested. Moreover, psychological stress has also been reported to affect the immune response. Thus, psychological factors are considered to influence the immune response, and an excessive immune response promotes the progression of arteriosclerosis, resulting in the development of coronary heart disease (CHD). In this study, the relationship between the immune response and psychological factors was investigated in CHD patients (n = 74) and normal controls (n = 64). Natural killer (NK) activity was significantly higher in the CHD group than the normal control (CHD vs normal: 8151.39 vs 6653.06, P < 0.05), and was significantly elevated by the suppression of anger and negative emotions (P < 0.05). These results indicate that the characteristic process of psychological response in CHD patients is related to an overresponse of NK activity. We speculate that this linkage significantly influences the development of CHD.