Rationale: Short-term exposure to air pollution has been associated with asthma exacerbation and increased healthcare use caused by asthma, but its effect on asthma mortality remains largely unknown. Objectives: To quantitatively assess the association between short-term exposure to air pollution and asthma mortality. Methods: We investigated 4,454 individuals who lived in Hubei province, China, and died from asthma between 2013 and 2018. A case-crossover design and conditional logistic regression models were applied for data analyses. Exposures to particulate matter <= 2.5 mu m in aerodynamic diameter (PM2.5), particulate matter <= 10 mu m in aerodynamic diameter (PM 1 to), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O-3) were estimated by inverse distance weighted averages of all monitoring stations within 50 km from each case's home address. Measurements and Main Results: Each interquartile range (IQR) increase of PM 2.5 (lag 3; IQR, 47.1 mu g/m(3)), NO2 (lag 03; IQR, 26.3 mu g/m(3)), and O-3 (lag 3; IQR, 52.9 mu g/m(3)) were positively associated with asthma mortality, with odds ratios of 1.07 (95% confidence interval, 1.01-1.12), 1.11 (95% confidence interval, 1.01-1.22), and 1.09 (95% confidence interval, 1.01-1.18), respectively. There was no evidence of departure from linearity for these associations. Further adjustment for other pollutants did not change the associations materially. We did not observe significant associations between PM10, SO2, and CO exposures and asthma mortality. Overall, the estimates remained consistent in various sensitivity analyses. Conclusions: Our results provide new evidence that short-term exposures to PM2.5, NO2, and O-3 may increase asthma mortality risk. Further studies are needed to confirm our findings in other populations.