Bornholm disease is generally attributed to infection with Coxsackie viruses of the B group, but in 1954-56 a number of sporadic cases occurred in Bytom, Upper Silesia, which were shown on virological examination to be caused by Coxsackie A4. In 1957, however, in the same area, an epidemic of Bornholm disease broke out for which Coxsackie B virus was clearly responsible. Re-examination of stocked material from the earlier sporadic cases to make sure that no B-type virus was present confirmed that these cases had been caused by A4. Clinically, the epidemic cases showed a preponderance of abdominal pains and comparatively infrequent chest pain, whereas the reverse was true of the sporadic cases; vomiting was also considerably less frequent in the sporadic than in the epidemic cases.