The dermatoglyphic configurations of 78 children with acute rheumatic fever were compared with those of 46 first-degree relatives and 1,310 normal subjects. Of the children with acute rheumatic fever, 75% had an ulnar deviation of the axial triradius. In about 40% of this group, the ulnar deviation was associated with a concomitant distal displacement, which resulted in a significantly higher mean maximal angle atd (P less than .001) and significantly lower mean ab and td ridge counts (P less than .001) relative to normal control values. The palmar dermatoglyphics of patients with acute rheumatic fever were more closely related to the configurations of first-degree relatives than to normal controls. The dermatoglyphic profiles of six patients were nearly identical to those of their first-degree relatives, all of whom had a history of acute rheumatic fever. Presence of abnormal dermatoglyphic profiles in a large proportion of children with acute rheumatic fever supports the hypothesis that certain individuals have a genetic predisposition to this disease.