Studying 122 patients who had been mechanically ventilated and no previous evidence of pneumonia at ICU of 103 Hospital from 1/2009 to 12/2011. The patients were divided in 2 group. The group 1 had 63 ventilator asociated pneumonia (VAP) patiens, and the group 2 had 59 patiens had been mechanical vetilation without VAP as control group. Determination of procalcitonin (PCT) concentration of blood at the time TO (right after admission to ICU), and at points of time: T1 (time of VAP diagnosed), and T3,T5,T7 (day 3th, 5th , 7th after VAP). Comparison of PCT in the 2 groups at Tl, monitoring changes of PCT at T3,T5,T7 in VAP group. The results showed: - Procalcitionin having small value in diagnosis of VAP patients. - Procalcitionin is able to predict the rate of dead in VAP patients. Monitoring the progress of PCT helps predict the treatment result.