The prevalence of obesity among Pacific Island adolescents is high and is a major health concern for Pacific Islanders. Yet there is limited data on effective obesity prevention strategies for this population. Also, previous studies suggest that widely used measures of obesity may not be valid for Pacific Island adolescents, indicating that there is a need to develop measures which apply to this population. This research will develop measures of body composition that are valid for Pacific Islanders. These will be applied to over 17,000 students in the Pacific Obesity Prevention in Communities (OPIC) study. Factors that predict obesity, direct measures of body composition and anthropometry measures of body composition will be identified. This research will help identify suitable areas for obesity prevention interventions and potential solutions to improve the health of Pacific Islanders.