Systemic non-Hodgkin's lymphoma can affect the myocardium, particularly in immunocompromised patients. When present, symptoms and signs are usually nonspecific, making the diagnosis of cardiac involvement very difficult before an autopsy. Ventricular arrhythmias are also unusual in this setting. We describe a case of secondary myocardial non-Hodgkin's lymphoma presenting with sustained monomorphic ventricular tachycardia and thickening of the basal interventricular septum. Complete remission of myocardial lesions was observed after completion of second-line chemotherapy treatment, without further recurrences of arrhythmias in eight months.