Objective To study the feasibility of using heat and moisture exchangers (HME)as an alternative to heated humidifiers (HH) in patients undergoing mechanical ventilation. Methods 266 pa-tients with mechanical ventilation admitted to our ICU over the recent 3 years were allocated to the experi-mental group (humidification with a heat and moisture exchanger) and the control group (with heated hu-midifier), and the effect of humidification, the reserved time of artificial airway, the time on mechanical yen-tilation, the time of stay in ICU, the ineidenee of ventilator-associated pneumonia (VAP) and the mor-tality rate were comparatively studied and analyzed. Results Significant differences were found between the experimental and the control group in effect of humidification, insufficiency of humidification or excessive hu-midification, airway spasm and time on mechanical ventilation and time of stay in ICU. The incidence of VAP in the control group was significantly higher than that in the experimental group. There were no significant dif-ference between the two groups in the reserved time of artificial airway and the mortality rate. There were no accident of humidification occurred in the experimental group while there were one case complicated with air-way burn and 11 eases complicated with choking with water in the control group. Conclusions We conclude that HH can be replaced by HME on mechanical ventilation while disease evolution and effect of humidification should be monitored closely and keep HME unobstructed.