Objective To study the separate and combined effects of environment,lifestyle,physical characteristics,blood biomarkers and genetic factors on aetiology of major chronic diseases in adult Chinese.Methods China Kadoorie Biobank (CKB) is a large blood-based prospective cohort study.The baseline survey took place in 5 urban and 5 rural areas across China during 2004-2008,with collection of data through questionnaire,physical examination and blood samples.Following the baseline survey,5％ of the randomly selected participants were surveyed in 2008,and repeated every 4-5 years.All participants would be followed for cause-specific mortality and morbidity through registries and for any hospital admission through linkages with health insurance databases.Results Overall,512 891 adults aged 30-79 years (mean 51.5) were recruited,including 41.0％ men and 55.9％ from rural areas.Blood collection was successfully done in 99.98％ of the participants.The prevalence of current regular smoking was 61.3％ in men and 2.4％ in women.The prevalence of regular alcohol consumption (i.e.,weekly) was 33.4％ in men and 2.1％ in women.At the baseline,41.8％ of men and 45.3％ of women were overweight or obese (i.e.,BMI≥24.0 kg/m2) and 32.2％ of men and 30.2％ of women were hypertensive (i.e.,SBP≥140 mm Hg or DBP≥90 mm Hg).For each of the main baseline variables,there were large variations on age,sex and areas of study.Conclusion CKB seemed to be a powerful and rich resource in studying the environmental and genetic determinants of major chronic diseases in the Chinese population.