Objective To investigate the characteristics of ventilator associated pneumonia (VAP)caused by Stenotrophomonas maltophilia(Sm)in ICU。Methods The clinical data of 39 patients with VAP caused by Sm，from Jan 2001 to Dec 2006，were retrospectively investigated．Results In 15 kinds of antibiotics sensitivity test，all cases showed 100％ resistance to 12 kinds of antibiotics except sulfamethoxazole／trimethoprim。ticarcillin／clavulanic acid and ciprofloxacin with sensitivity rate of 46．2％ ， 30．8％ and 12．8％ ．respectively．92．30％ of Sm VAP were CO—infected with other microorganisms and 79．5％ of VAP were late-onset．The use of broad-spectrum antibiotics．especially carbapenem．and prolonged mechanical ventilation more than 7 days were risk factors for Sm VAP．Morbidity of Sm VAP was 87．2％ ．Conclusions Sm VAP has an important role in ICU infections with high morbidity and CO-infection rate．It should be alerted to the possibility of Sm VAP in the case of when prolonged ventilation (gt;7 days)or carbapenem is used．