Introduction : Acute respiratory distress syndrome (ARDS) is characterized by acute lung injury, noncardiogenic pulmonary edema, and severe hypoxia. The present study aimed at early diagnosis of ARDS using FOB to study mediators in BAL; calculation of the incidence of pulmonary infection among ARDS patients; and the microbiological study of BAL for these patients. Patients & Methods : This research follows a prospective study design, thirty adult hypoxic patients needing mechanical ventilation constituted the study population. A consecutive sampling technique was followed to include those patients as the study sample. Results : Based on the results of the presents study, the following can be concluded:- 1) The FOB is a useful tool that can used for early diagnosis of ARDS. 2) Early predictor variables associated with high probability of developing ARDS include: a)High ALI score, b) High APACHE III score, c) High BAL IL-8, d) High BAL TNF-alpha, e) Low BAL G-CSF, f) Low BAL GSH. 3) Non-predictor variables for ARDS include: a) BAL IL-10, b) BAL TGF-beta.