Abstract Varying degrees of heart block may occur in the presence of congenital heart disease, and cause mild Stokes-Adams attacks which conceivably could be more severe, with convulsions. The symptoms then are not due to the congenital heart disease but to the cerebral anoxia that follows the ventricular standstill. This condition may occur in congenital heart disease where no evidence of an interventricular septal defect is apparent. A case is presented with definite evidence of a patent ductus arteriosus, and no evidence of a patent interventricular septum, in which mild Stokes-Adams attacks occurred associated with the sudden onset of heart block, which varied in degree, was transient and followed by normal rhythm. This occurred following exertion, and was not of nervous origin. This is the first case to be reported of congenital heart disease with Stokes-Adams attacks in which an electrocardiogram taken during the attack is presented.