We present 2 cases with severe necrotizing pneumonia due to community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection. The patients were a 89-year-old man and a male student of 15 years of age. Chest X-rays and CT scans demonstrated multiple consolidations with cavitary lesions showing necrotizing pneumonia. MRSA strains were isolated from the sputum cultures on admission in these patients who did not have any established risk factors for MRSA infections such as history of hospitalization, surgery, hemodialysis, the presence of a permanent indwelling catheter or percutaneous medical device, and residence in a long-term care facility. These patients thus satisfied the international criteria for CA-MRSA presented by the Centers for Disease Control and Prevention (CDC). Unfortunately, the first case died of CA-MRSA pneumonia in spite of intensive treatments including anti-MRSA antibiotics. Unlike the severe CA-MRSA cases in western countries, Panton-Valentine leukocidin (PVL) genes were not detected in the present cases, suggesting that factors other than PVL had a significant effect on the severity of necrotizing pneumonia. To the best of our knowledge, this is the first report of severe necrotizing pneumonia caused by CA-MRSA in Japan.