Staphylococcus aureus has been implicated as a cause of antibiotic-associated diarrhea; however, reports rarely originate from the United States. We report 5 cases of antibiotic-associated diarrhea caused by methicillin-resistant S. aureus (MRSA). Eighty percent of the stool specimens were greenish. Heavy growth of MRSA from greenish stool culture may warrant oral vancomycin therapy.