This report describes the case of a 33-year-old woman with biopsy-proven, active lymphocytic myocarditis manifested by intractable ventricular tachycardia, nonspecific intraventricular block, and myocardial dysfunction. We treated hersuccessfully with OKT3 monoclonal antibody and antiarrhythmic agents. Immunosuppression is not recommended in patients with infectious or postinfectious myocarditis. However, it may have an important role in autoimmune myocarditis. In the few reports in the medical literature that we were able to find, OKT3 monoclonal antibody was administered early in the setting of acute, fulminant autoimmune myocarditis. Our patient received OKT3 therapy in a later phase of the disease, when inflammatory infiltrates were accompanied by extensive fibrosis and severe damage of cardiomyocytes. Our patient had concomitant Helicobacter pylori infection and a strong positive family history of gastric cancer, a disease often associated with H. pylori. We discuss the possibility of a causal relationship between H. pylori infection and autoimmune myocarditis.