Globally, obesity and physical inactivity are two health issues affecting young people. In New Zealand, the most current statistics indicate that 33.6% of 11 to 14 year olds, and 27% of 15 to 18 year olds, are considered overweight or obese.1,2 Despite these high prevalence levels, only 38% of young people aged 13 to 17 years in New Zealand are considered physically inactive.3 Future effort needs to be directed towards enhancing the existing national surveys to ensure a comprehensive and valid surveillance system of adolescent obesity and inactivity is conducted on a regular basis. This would involve the development of age, sex, and ethnic specific body mass index cut-off thresholds to define overweight and obesity, validation of an adolescent questionnaire that examines physical activity from a broad perspective, and development of physical activity recommendations for youth based on international best practice. Although the main focus of this paper is on obesity and physical inactivity, diet is also a key determinant of obesity. Therefore, to provide an accurate assessment of factors associated with youth obesity in New Zealand, surveillance of diet must occur concurrently with that of obesity and physical activity. The development of accurate measurement tools is critical for (1) determining obesity and inactivity trends, (2) identifying at-risk groups, (3) tracking progress toward national health priorities, and (4) evaluating the efficacy of interventions targeting obesity and physical inactivity. Furthermore, attention needs to be directed towards identifying correlates of inactivity and obesity to help inform the development of comprehensive multisectorial, multisetting, prevention, and management initiatives.