The prevalence of overweight and obesity has been rapidly increasing within countries of the Asia-Pacific region, with adverse consequences for health. The Obesity in Asia Collaboration (OAC) was initiated to provide reliable evidence concerning the relationships between anthropometrical markers of adiposity with cardiovascular risk factors within, and across, ethnic groups. This is to be achieved through the collection of cross-sectional studies from the Asia-Pacific region. These data will be used to examine the ethnic-specific associations of different anthropometric measures of adiposity (such as body mass index, waist circumference, waist-hip ratio and waist-height ratio) with cardiovascular risk factors (fasting blood glucose and blood pressure). Estimates of the relative risks for type 2 diabetes and hypertension with increased adiposity will be obtained using data from contributing studies in conjunction with those from the previously established Asia Pacific Cohort Studies Collaboration. To date, 12 countries and regions from the Asia-Pacific region with information on nearly 300,000 individuals, are participants in the OAC. Data from other eligible studies are sought. The findings from the OAC will provide reliable evidence concerning the association of adiposity with cardiovascular risk factors across ethnic groups. It will also provide a strong evidence base upon which to define ethnic-specific cut-points for overweight and obesity.