A particularly extensive epidemic of Coxsackie B3 virus infection occurred in Johannesburg in the spring and summer of 1984. A total of 142 positive cases were diagnosed by isolation of the virus from stools and other specimens (60) or by serology (82). Coxsackie B3 accounted for 87% of the isolations and was also the dominant serotype on serology. The outbreak involved predominantly children and young adults, with no apparent sex differences being noted. The majority of specimens came from the white population and no significant difference in age or sex distribution could be observed between the two race groups. The major clinical presentation in the white group was Bornholm disease followed by cardiac involvement and then meningoencephalitis. In the black group, however, myocarditis was the major clinical presentation, which is of particular interest taking into account the extremely high incidence of acute rheumatic carditis in this population and the prevalence of chronic cardiomyopathy.