The potential number of individuals who might benefit from a cardiac replacement procedure (either cardiac transplantation or insertion of a total artificial heart) was retrospectively estimated from medical records for residents of Olmsted County, Minnesota, who had died during a 5-year period. Residents were divided into two age groups: those younger than 15 years (pediatric) and those 15 to 69 years (adult). During the 5-year period of observation, cardiac disease led to death in 17 of the 8342 live births in Olmsted County. Cardiac disease also caused the deaths of 248 adults meeting the age criteria. Five children and 35 adults met all criteria for cardiac replacement. Extrapolation to the total population of the United States suggests that 2167 children (a 95% confidence interval of 361 to 3972) and 16,500 adults (a 95% confidence interval of 11,456 to 22,959) per year could potentially benefit from cardiac replacement.