The recent resurgence of rheumatic fever reported in eight locations in the United States after years of decline has several noteworthy characteristics. Most patients were children of families in high- to middle-income brackets with ready access to medical care. In four of the outbreaks, the majority of patients were adults, who were more likely than children to have arthritis and less likely to have Sydenham's chorea. Many patients had no clinical history of streptococcal pharyngitis. Rheumatic fever developed in some patients despite antibiotic treatment for streptococcal pharyngitis. Analysis of the outbreaks supports the following conclusions: No population is exempt from rheumatic fever. Physicians should be diligent in performing throat cultures in cases of suspected streptococcal pharyngitis. The efficacy of orally administered penicillin in preventing rheumatic fever should be reexamined, and oral antibiotics that are potentially more effective should be sought.