Overweight/obesity is the most prevalent disease among U.S. youth, and overweight youth have an increased risk of becoming overweight adults. Improving health knowledge and behaviors during childhood may be one mechanism for reducing the burden of overweight/obesity. Healthy Hearts was developed as an interdisciplinary internet-based learning instructional module designed to improve health behaviors in children in the fifth and sixth grade. The purpose of this analysis was to assess the effectiveness of the Healthy Hearts module in teaching cardiovascular health knowledge. Cardiovascular health knowledge was assessed pre- and post-module. Independent t-tests were used to compare pre- and post-test scores. Pearson product moment and Spearman rank order correlations were used to identify significant bivariate relationships. Stepwise multiple regression analysis was used to identify the significant independent predictors of test score improvement. This study included 126 elementary school classes (mean children). Represented were 2312 children (M1334, F1376) from 10 states with a mean age of 11 (+1) years. Average participation was 14 (+9) students (77%) from each class. Pre- and post-test scores were 58% (+24) and 76% (+20), respectively. Mean improvement was 19% (+32). Girls scored significantly better than boys on the pre-test (4.14 v. 3.91, p=0.001); however, this discrepancy disappeared post-test. Additionally, boys score improvement was significantly greater than girls (21% v. 18%, p=0.01). Gender (r=-0.053, p=0.011) and age (r=-0.091, p<0.001) were significantly correlated with improvement in score. Age, sex, and pre-test score were significant independent predictors of change in score, accounting for 59% of its variance. These results indicate that the Healthy Hearts e-learning module is effective in improving cardiovascular health knowledge. Additionally, there may be gender differences in both general cardiovascular health knowledge and the acquisition of this knowledge. It appears that the boys in this study exhibited a deficit in cardiovascular knowledge when compared to girls. This may be an important area for future research given the gender differences in cardiovascular disease morbidity and mortality. Keyword(s): elementary education, research, technology