Rapid economic developments accompanied by environmental and lifestyle changes over the last 3 decades in China have resulted in dramatic increases in the incidence of chronic diseases such as cancer and cardiovascular disease. As a result, cancer and cardiovascular disease are two of the leading causes of death in China. This change in disease spectrum presents an enormous challenge to public health practitioners and policy makers in designing cost-efficient strategies for disease prevention. To identify reasons for the increased risk of chronic disease in China and investigate etiologic hypotheses that cannot be adequately evaluated in other populations, we launched the Shanghai Women's Health Study in 1996 and the Shanghai Men's Health Study in 2001. In collaboration with community health workers, the Shanghai Women's Health Study recruited 75 049 women aged 40–70 from 7 communities in urban Shanghai between 1997 and 2000 with an overall response rate of 92%. Using a similar protocol, the Shanghai Men's Health Study recruited 61 500 men aged 40–74 from 8 communities in Shanghai with a response rate of 75% for study participation. Biological samples were collected from the vast majority of study participants. All study participants were interviewed using a structured questionnaire to obtain information related to their usual dietary intake, physical activity, and other lifestyle factors. These two cohorts are being followed through a combination of biennial in-person surveys and record linkage with the Shanghai Cancer Registry and Shanghai Vital Statistics database. In addition to ascertaining health outcomes, we also obtain exposure data as part of the follow-up surveys.