Nodal rhythm is one of the less common disorders of the cardiac mechanism. It may occur as a functional disturbance secondary to altered vagal tone and as such may appear after the administration of digitalis or atropine. It is occasionally encountered in arteriosclerotic heart disease, and a few authors have reported its occurrence in acute rheumatic fever. In 1937 Cutts1 reported 12 cases of interference dissociation, a variety of nodal rhythm, of which 6 were associated with acute rheumatic fever and 1 with tonsillitis. He stated that reports in English on nodal rhythm and interference dissociation have not mentioned rheumatic fever as an important cause. McMillan and Cook2 reported 2 cases of nodal rhythm occurring in the course of rheumatic fever, in 1 of which, however, digitalis had been administered. Bain3 described the case of a patient suffering from rheumatic fever who exhibited auricular fibrillation, reciprocal rhythm,