Cardiovascular disease is the number one killer of men and women in North America. Male BALB/c mice infected with coxsackievirus B3 (CVB3) develop more severe inflammatory heart disease compared to female mice, similar to the increased heart disease that occurs in men. We show here that increased inflammation in male mice is not due to increased viral replication in the heart, but associated with increased proinflammatory cytokines IL-1beta, IL-18 and IFN-gamma. We have previously reported that IL-12Rbeta1 signaling increases CVB3-induced myocarditis and IL-1beta/IL-18 levels in males, while IL-12(p35)/STAT4-induced IFN-gamma does not alter the severity of acute disease. However, whether differences exist between males and females in these two cytokine signaling pathways is unknown. In this study, we examined sex differences in 1) IL-12Rbeta1 signaling or 2) STAT4/IFN-gamma pathways following CVB3 infection in BALB/c mice. We found that male and female mice deficient in IL-12Rbeta1 had decreased inflammation and viral replication in the heart, indicating that IL-12Rbeta1 signaling increases myocarditis in both sexes. In contrast, STAT4 deficiency did not alter the sex difference in myocarditis, with males maintaining increased inflammation over females. IFN-gamma deficient males, however, had decreased myocarditis and viral replication compared to females. Thus, IFN-gamma increases inflammation in males independent from STAT4. These results demonstrate that sex differences greatly influence viral replication and the severity of acute CVB3-induced myocarditis.