This study was undertaken to determine whether there was a correlation between fine particles (PM2.5) levels and hospital admissions for myocardial infarction (MI) in Taipei, Taiwan. Hospital admissions for MI and ambient air pollution data for Taipei were obtained for the period 2006-2010. The relative risk of hospital admissions for MI was estimated using a casecrossover approach, controlling for weather variables, day of the week, seasonality, and longterm time trends. For the single-pollutant model (without adjustment for other pollutants), increased numbers of MI admissions were significantly associated with higher PM2.5 levels both on warm days (>23°C) and on cool days (<23°C). This was accompanied by an interquartile range elevation correlated with a 10% (95% CI = 6-15%) and 5% (95% CI = 1-9%) rise in number of MI admissions, respectively. In the two-pollutant models, PM2.5 remained significant after inclusion of SO2 or O3 on both warm and cool days. This study provides evidence that higher levels of PM2.5 increase the risk of hospital admissions for MI.