The infection withToxoplasmosisin humans, especially in people with weak immune system, pregnant women and those with underlying disease could entail serious damage. The objectives of this study are to calculate the prevalence ratio of Toxoplasma gondiiinfection in heart disease patients and assess important role of interleukin-10 in immune regulation. About 150 blood samples werecollectedfrom heart disease patients in Thi-Qar province and about 100 blood samples were collected from apparently healthy controls. Enzyme linked immunosorbantassayTest (ELISA) was used to test sera of patients and controls to detect anti-Toxoplasma Abs (IgG&IgM). While the positive samples with toxoplasmosis were tested to detect the levels of IL-10 and IL-12. The overall estimated seroprevalence was 46% in heart disease patients are higher than those in apparently healthy controls 20%, and there was a significant difference between them. The results of interleukins elucidated high levels of IL-12 82.85 pg/ml in heart disease patients infected with toxoplasmosis when compared with control 60.97 pg/ml, and there was significant difference between them. While there was no significant difference in IL-10 in both patients and controls. Also found a significant difference between female and male in patients and controls, in male was higher than those in female.The increased level of IL-12 in patients and controls with toxoplasmosis indicate to the activity of immune system in those patients.