this study evaluated the association between the risk of events requiring ambulance services and the ambient temperature and particulate matter of 2.5 μm (pM 2.5 ) and 10 μm (pM 10 ) for populations living in subtropical Taiwan. We used a distributed lag nonlinear model with a quasi-Poisson function to assess the roles of ambient temperature, PM 10 and pM 2.5 in the use of ambulance services for respiratory distress, coma and unconsciousness, chest pain, lying down in public, headaches/dizziness/vertigo/ fainting/syncope and out-of-hospital cardiac arrest (OHCA). The relative risk (RR) and 95% confidence interval (CI) of each specific event were calculated in association with the ambient conditions. In general, the events that required ambulance services had a V-shaped or J-shaped association with the temperature, where the risks were higher at extreme temperatures. The RR of each event was significant when the patients were exposed to temperatures in the 5 th percentile (<15 °C); patients with OHCA had the highest adjusted RR of 1.61 (95% CI = 1.47-1.77). The risks were also significant for coma/ unconsciousness, headaches/dizziness/vertigo/fainting/syncope, and OHCA but not for respiratory distress, chest pain and lying down in public, after exposure to the 99 th percentile temperatures of >30 °C. The risks for use of ambulance services increased with PM exposure and were significant for events of respiratory distress, chest pain and OHCA after exposure to the 99 th percentile pM 2.5 after controlling for temperatures. Events requiring ambulance services were more likely to occur when the ambient temperature was low than when it was high for the population on the subtropical island of Taiwan. The association of the risk of events requiring ambulance services with PM were not as strong as the association with low temperatures.The increased frequency and intensity of extreme climate events are important public health concerns 1 . Studies have reported that ambient temperature and air pollution are important factors with significant impacts associated with various morbidities and mortalities [2][3][4] . The associations between mortality and the temperature have been characterized by U-shaped, V-shaped and J-shaped curves 5,6 , with mortality increasing at extremely cold and/or extremely hot temperatures 7,8 . Studies have also found that the risk of emergency room visits for out-of-hospital cardiac arrest (OHCA) was greater in cold seasons than in hot seasons 9-11 . In Taiwan, the cumulative 6-day relative risk of emergency room visits for OHCA reaches 1.73 when the mean temperature is 14 °C in comparison to when it is >27 °C after controlling for air pollution 12 .Climate conditions have important impacts on the transport and dispersion of air pollutants. The role of pollutants in health impacts may thus vary with climate conditions 13 . However, studies may emphasize the impacts of air pollution rather than temperature on health, especially for respiratory diseases. One study that used the Danish Diet, Cancer, ...