BACKGROUND: The link between particulate air pollution and cardiovascular (CVD) mortality has been investigated. However, there is little direct evidence that reduction measures which decrease particulate air pollution would lead to a reduction in CVD mortality. OBJECTIVES: In Beijing, China, air quality improvement strategies were developed and actions were taken before and during the 2008 Olympic and Paralympic Games. Taking advantage of this opportunity, the aim of the study was to assess the effects of changes in particulate air pollution before (May 20-July 20, 2008), during (August 1-September 20, 2008) and after (October 1-December 1, 2008) the Olympics period. METHODS: Concentrations of air pollution, meteorology and CVD death counts were obtained from official networks and monitoring sites located on the Peking University campus. Air pollution effects with lags of 0-4 days as well as of the 5-day average on cause-specific CVD mortality were investigated for the complete study period (May 20-December 1, 2008) using Quasi-Poisson regression models. Different gender and age subgroups were taken into account. Additionally, effect modification by air mass origin was investigated. In a second step, air pollution effects were estimated for the three specific periods by including an interaction term in the models. RESULTS: We observed large concentration decreases in all measured air pollutants during the unique pollution intervention for the Beijing 2008 Olympics. For the whole period, adverse effects of particulate air pollution were observed on CVD mortality with a 1-day delay as well as for the 5-day average exposure, e.g. an 8.8% (95%CI: 2.7-15.2%) increase in CVD mortality with an interquartile range increase in ultrafine particles. The effects were more pronounced in females, the elderly and for cerebrovascular deaths, but not modified by air mass origin. The specific sub-period analysis results suggested that the risks of CVD mortality were lowest during the Olympic Games where strongest reduction measures have been applied. CONCLUSIONS: The results indicated that the reduction of air pollution due to air quality control measures led to a decreased risk of CVD mortality in Beijing. Our findings provide new insight into efforts to reduce ambient air pollution.