Gerrard P. Accuracy of self-reported physical activity as an indicator of cardiovascular fitness depends on education level. To determine whether there is a relationship between the level of education and the accuracy of self-reported physical activity as a proxy measure of aerobic fitness. Data from the National Health and Nutrition Examination from the years 1999 to 2004 were used. Linear regression was performed for measured maximum oxygen consumption (V̇o 2 max) versus self-reported physical activity for 5 different levels of education. This was a national survey in the United States. Participants included adults from the general U.S. population (N=3290). None. Coefficients of determination obtained from models for each education level were used to compare how well self-reported physical activity represents cardiovascular fitness. These coefficients were the main outcome measure. Coefficients of determination for V̇o 2 max versus reported physical activity increased as the level of education increased. In this preliminary study, self-reported physical activity is a better proxy measure for aerobic fitness in highly educated individuals than in poorly educated individuals.