The aim of the current study was to investigate the impact of 3 atmospheric pollutants, PM2.5, SO2, and O-3-8h, on M. pneumoniae infection risks during warm and cold seasons in Shengyang, China. The relationship between daily average concentrations of PM2.5, SO2, and O-3-8h, between April 1, 2013, and March 31, 2016, and M. pneumoniae-positive patients in the Department of Pediatrics and Respiratory Clinic were analyzed via Spearman's correlation analysis. A time-series Poisson regression generalized additive model (GLM) was used to analyze risks for testing positive for M. pneumoniae, associated with differences in PM2.5, SO2, and O-3-8h concentrations during warm and cold seasons (1). Daily average concentrations of these 3 atmospheric pollutants were related to the number of patients testing positive for M. pneumoniae (P<0.05). The relationship was stronger for females than males. The relationship was stronger for patients with positive results (P<0.01) than patients with negative results (P<0.05). Pediatric outpatients (under 15 years of age) showed a stronger relationship to PM2.5 (P<0.01). Patients over 15 years of age (respiratory clinics) showed a stronger relationship to SO2 and O-3-8h (P<0.01) (2). Average daily concentrations of PM2.5, SO2, and O-3-8h exhibited different characteristics. Increased risks for M. pneumoniae infections were related not only to mass concentrations of atmospheric pollutants, but also to physiological doses of atmospheric pollutant particles.