The intervention was a 10-12 week (twice a week) after-school program including a pilot (with 2 experimental schools) and main intervention (6 schools each including control and experimental groups). Each session consisted of health education taught by a Community Health Worker, based on the bilingual BienEstar ('Well-Being') curriculum, and physical activity based on the Coordinated Approach to Children's Health (CATCH) curriculum. Main outcome variables were Body Mass Index (BMI), aerobic capacity health knowledge and healthy intentions. Participants (n=1,103) were predominantly socio-economically disadvantaged Hispanic 3rd to 5th graders. At baseline, 21.6% of children were overweight and another 25.6% obese. The intervention was successful in recruitment, implementation and retention of participants. The pilot study (n=172) found a significant BMI reduction and increased aerobic capacity. In the main intervention, experimental group participants (n=323) reduced their BMI, but this reduction was not significantly larger than the control group (n=608). Intervention group participants significantly increased their healthy nutrition intentions compared to control group participants, but not health knowledge. While the findings in regards to changes in health indicators were modest, all findings were in the expected direction. The current project provides evidence for a strong need and desire to participate in projects that are accessible and address primary prevention of chronic diseases within a population that has a high prevalence of risk factors and limited access to care.