Our study were conducted on 54 mechanically ventilations patients in Critical Care Department from July 2000 till Dec 2001 aiming at evaluation of the value of Bronchoalveolar lavage fluid LDH and ALP enzymes and cellular profile (total cell count, aleveolar macrophages, polymorphnuclear neutrophills) in differentiation between infectious and non infectious pulmonary disorders and we found that total LDH activity and ALP activity, total cell count and polymorphnuclear neutrophlare higher in infectious pulmonary disorders and non infectious pulmonary diseases.