During the first half of this century rheumatic fever was a common disease with significant morbidity and mortality in the United States. In the 1980s, when many clinicians were hoping this disease was a disease of the past, anxieties were renewed when outbreaks were reported in several areas around the country. Although the etiology still eludes us, insight has been gained. Environmental and genetic factors are believed to play a role in the epidemiology of this disease. Additionally, the implicated organism, the group A streptococcus, has many strains, and differences in its many proteins may determine their potential for rheumatic fever. The mechanisms leading to disease are not clear, but the streptococcus has been implicated as a source of antigens with cross-reactivity with human tissues and has been shown to modify immune mechanisms. Clinical aspects are briefly reviewed and physicians are reminded to consider rheumatic fever as a diagnostic possibility in the appropriate settings.