Objective To assess the effects of two different methods on differential cell count and the detection on inflammatory mediators in the process of induced sputum. Methods Induced sputum samples from outpatients with respiratory diseases were collected. Each sample was equally divided into two parts. One portion was processed at a regular way by incubation at 37 ℃ for 15 min in 0.1% dithiothreitol (DTT). Another was processed at 0 ℃ for 60 min in 0.1% DTT. The cell pellet was used for the cytology analysis by HE staining. The levels of IL-4,IL-5 and IL-8 were measured by Elisa Kit. Results Induced sputum was successfully collected from 20 subjects with chronic airway diseases ,including 7 males and 13 females . Total cell counts was lower in 0 ℃-incubated group than in 37 ℃-incubated group(P < 0.05). However,there was no difference in differential cell counts between two groups ,as well as the levels of IL-4 ,IL-5 and IL-8 in sputum supernatants(all P >0.05). Conclusions Except a difference in the total cell number ,there was no difference between two methods on the differential cell count and levels of certain inflammatory mediators.