Background. Increased cardiac stress, hypoxemia, and inflammation may contribute to acute cardiac events, such as myocardial infarction (MI), arrhythmia, and/or congestive heart failure (CHF). We sought to determine the incidence of such events in patients who were hospitalized for community-acquired pneumococcal pneumonia. Methods. We studied the medical records of all patients who were admitted for pneumococcal pneumonia during a 5-year period (2001-2005) to identify those who had MI, atrial fibrillation or ventricular tachycardia, or new-onset or worsening CHF at the time of hospital admission. Results. Of 170 patients, 33 (19.4%) had ≥1 of these major cardiac events. Twelve had MI, of whom 2 also had arrhythmia and 5 had new-onset or worsening CHF. Eight had new-onset atrial fibrillation or ventricular tachycardia; 6 of these also had new CHF. Thirteen had newly diagnosed or worsening CHF, without MI or new arrhythmias. Hypoxemia and anemia were prominent. Importantly, patients with concurrent pneumococcal pneumonia and cardiac events had a significantly higher mortality than those with pneumococcal pneumonia alone (P < .008). The coexistence of pulmonary and cardiac disease was often overlooked by admitting physicians who, seeking a unifying diagnosis, emphasized one diagnosis to the exclusion of the other. Conclusions. Patients with pneumococcal pneumonia are at substantial risk for a concurrent acute cardiac event, such as MI, serious arrhythmia, or new or worsening CHF. This concurrence significantly increases mortality due to pneumonia. Admitting physicians tend to seek a unifying diagnosis, but the frequent coexistence of pneumonia and cardiac events indicates the importance of considering multiple diagnoses.