Mothers' descriptions of their childrens' congenital heart disease were compared with cardiologists' diagnoses. Maternal understanding was examined with respect to 21 factors using bivariate contingency tables and multiple regression analyses. Of 285 mothers, 36% demonstrated poor comprehension. Maternal understanding was associated with sociodemographic variables but not with factors related to stress. All variables taken in concert that were predictive of understanding explained less than 13% of the variability in maternal knowledge. Distorted perceptions of congenital heart disease may cause unnecessary anxieties, inappropriate restrictions, and impairment of the child's self-perception. The bizarre nature of some of the mothers' incorrect descriptions and the accuracy of responses of mothers in biologic and health care occupations suggest that fundamental ignorance of the cardiovascular system may be of such importance as to minimize the impact of other variables.