Objective-To examine the secondhand smoke (SHS) exposure level in Chinese office buildings and to evaluate the effectiveness of a smoke-free policy in reducing SHS exposure.Methods-Survey of smoking policies and measurement of SHS level in 14 office buildings from 10 provinces in China.Results-Smoking in the building significantly elevated the SHS concentrations both in offices with at least one smoker and in offices with no smokers. In one building that recently adopted a smoke-free policy, the nicotine concentrations decreased significantly after the policy was enacted. Enactment of a smoking policy was effective in reducing SHS exposure in the buildings.Conclusions-Nonsmoking office workers in China were exposed to significant levels of SHS at work; both the central and local governments should realize the need to legislate against workplace smoking."The Tobacco Monopoly Act of the People's Republic of China" passed in 1991 requires that smoking should be banned or restricted in public places and on public transportation. "The Act for Protection of Minors" (1991) stipulates that no smoking is allowed in classrooms or dorms of middle schools, elementary schools, and kindergartens. In 1997, the central government drafted its first legislation that banned smoking in public transportation and its waiting areas. 1 Many provinces and cities also passed their own regulations. In 1993, Suzhou of Jiangsu Province became the first city in the country to ban smoking in all public places. By October 2006, 46% of all cities in China had passed regulations banning smoking in public places. The coverage of these local regulations went beyond public transportation and associated waiting areas, which are stipulated by the national law, to encompass most of the public places, including cinemas, museums, shopping malls, pubs, hospitals, kindergartens, and schools. 1 Compared with smoking in public places, workplace smoking has scarcely been mentioned in the law in China. There are cases of voluntary adoption of smoke-free policies at work, typically in certain professions, such as among health care institutions, but to date, there has been no regulation at any government level restricting workplace smoking in China. A typical worker spends 8 hours a day at work, and studies have shown that the work-place is one of the most important sources of secondhand smoke (SHS) exposure for nonsmokers. CDC offices, hospitals, and university hospitals around the country ban smoking in their premises. Some institutes already had a smoke-free policy in place before the proposal, and some others signed the proposal to adopt the policy. Nevertheless, China CDC has no administrative control over most of the institutes mentioned above. In the end, only a minority of the institutes signed the proposal, and most were left without a smoking policy. To investigate the degree to which such a smoke-free policy has achieved its desired goal of protecting the health of non-smokers at work, we compared the SHS level across fourteen health-related...