Community-associated methicillin-resistant Staphylococcus aureus is a frequent cause of skin and soft-tissue infections and is increasingly identified as a cause of pneumonia in immunocompetent patients. Panton-Valentine leukocidin, one of several leukocytotoxic peptides secreted by these cocci, is associated with increased virulence. A cluster of 3 unrelated patients with fatal pneumonia presumably caused by community-associated methicillin-resistant S aureus positive for Panton-Valentine leukocidin were treated in a 3-week period. Despite aggressive care and appropriate, timely administration of antibiotics, all 3 patients died. This article reviews the clinical and laboratory features suggestive of this lethal isolate, including unique findings on Gram stains of sputum.