The aim of this study is to evaluate the air pollution due to smoking in an office where no smoking control measures have been adopted. The concentration of suspended particulates (SP) at 8 points in this office were measured and the change of SP concentrations at 3 points were recorded for 24 hours. The results show that the main source of SP is tobacco smoke in the office. Smoking control measures should be promoted in such offices where smokers and non-smokers work together. The effectiveness of a ventilation system and practical smoking control measures are discussed.