Capillary changes in rheumatic fever have been reported. There is evidence for increased capillary permeability (Wilson, 1940; Pratesi and Garofoli, 1952). Coburn (1933) found postmortem evidence that rheumatic fever was associated with diffuse hemorrhagic changes. Costero (1949) demonstrated at autopsy cerebral capillary hemorrhages in acute rheumatic fever. There is also a well-known connection between a tendency to nose-bleeds and rheumatism (Levine and co-workers, 1930). During capillary microscopy of the nailbed as a routine clinical examination and as a research tool (Davis, 1946; 1953) a particular capillary pattern was seen recurring in rheumatic fever and rheumatic heart disease. It was decided to study this pattern and compare its incidence in rheumatic fever and rheumatic heart disease with that in control patients. Likewise, the conjunctival capillaries were studied systematically by use of the slit-lamp (J. L.). METHODS The technique of capillary microscopy at the nailbed and the normal pattern have been described