Ambient fine particulate matter (PM2.5) exposure has been linked to decreased semen quality, but the associations between PM2.5 constituent exposures and semen quality remain unknown. We enrolled 1081 men whose partners underwent assisted reproductive technology procedures in Wuhan, China in 2014-2015, and examined their semen quality. Daily average concentrations of PM2.5 constituents including 10 metals/metalloid elements and 4 water-soluble ions were continuously determined for 1 week per month at 2 fixed monitoring stations. Linear mixed models were used to examine the associations of exposures to PM2.5 and its constituents with semen quality. Each interquartile range (36.5 mu g/m(3)) increase in PM2.5 exposure was significantly associated with 8.5% (95% CI: 2.3%, 14.4%) and 8.1% (95% CI: 0.7%, 15.0%) decrease in sperm concentration and total sperm number, respectively. Antimony, cadmium, lead, manganese, and nickel exposures were significantly associated with decreased sperm concentration, whereas manganese exposure was also significantly associated with decreased total motility. Nonsmokers were more susceptible to PM2.5 constituent exposures, especially for antimony and cadmium (all P for effect modification <0.05). These findings suggest that PM2.5 and certain constituents may adversely affect semen quality, especially sperm concentration, and provide new evidence to formulate pollution abatement strategies for male reproductive health.