The purpose of this quantitative study was to examine the relationship between physical fitness, body mass index and academic performance in Hispanic children enrolled in grade 5 from a district in the Rio Grande Valley. A total of 547 participants were selected from 11 elementary schools from a school district in the Rio Grande Valley. The dependent variable, academic performance, was measured by children's gain score on the STAAR Progress Measure for Reading and Math assessments. The independent variables of physical fitness were measured by scores on cardiovascular fitness and body mass index from the FITNESSGRAM assessment. The literature review on the Conceptual Framework, Theoretical Model to Improve Health and Academic Performance, was identified as the framework for this study. This framework was based on a model of factors associated with improved health and academic performance. The factors included the correlation between physical activity, fitness, fatness, and academic achievement. The method of statistical and data analyses was multiple regression. The results revealed that body mass index was correlated with academic performance. Body mass index accounted for a statistically significant variance in math gains while time did not explain any significant variance in math. There was no correlation between reading gains and time and body mass index. The results by weight group revealed a significant correlation between time and reading gains for the normal weight group and a significant correlation between body mass index and math gains for the obese group. The results by gender revealed a positive and significant correlation between body mass index and math gains for females. These results suggest that at grade 5, consideration be given to body mass index levels of Hispanic children from low-income backgrounds. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]