Abstract: Objective To investigate the roles of IQ motif containing GT Pase activating protein 1(IQGAP1)and cell division cycle 42 protein(Cdc42)in the repair of the injured airway epithelial cells(AECs)at different stages.Methods Twenty-four Kunming mice were randomly divided into four groups as following:3,7,60-day formaldehyde(FA)inhalation group and the control group.The mice were exposed to gaseous FA of 5 mg/m3 for 4h/day for 3,7,and 60 days.The expressions and locaiizations of IQGA P1 and Cdc42 protein in the AECs were observed during the repair.Results IQGAP1 of the 3-and 7-day groups significantly incr eased(P<0.01),but decreased at the 60th day.Cde42 protein obviously decreased after 3-day inhalat ion of FA(P<0.01),but enhanced again at the end of 7th day.IQGAP1 localized around the plasma membrane and Cdc42 protein mainly distributed uniformly in the cytoplasm of A ECs.In 3-and 7-day treated groups they were co-localized at the cell leading edge,and in 60-day treated group their localizations were similar to the control.Conclusion During the injury and the repair after the injury,the expr ession and the localization of IQGA P1 and Cdc42 protein are dynamically changed in the AECs.They may play a key role in the repair process of airway epithelium injury.