Background : Patients with established ARDS have a mortality rate that exceeds 50 percent despite of intensive care including artificial ventilation modality, Mortality has been associated with sepsis and organ failure preceding or following ARDS ; APACHE II score ; old age and predisposing factors. Revised ventilator strategy over last 10 years especially at ARDS appeared to improve the mortality of it. We retrospectively investigated 40 ARDS patients of respiratory-care unit to examine how these factors influence outcome. Methods : A retrospective investigation of 40 ARDS patients in respiratory-care unit with ventilator management over 46 months was performed. We investigated the clinical characteristics such as a risk factor, cause of death and mortality, and also parameters such as APACHE II score, number of organ dysfunction, and hypoxia score (HS, $PaO_2/FIO_2$) at day 1, 3, 7 of severe acute lung injury, and simultaneously the PEEP level and tidal volume. Results : Clinical conditions associated with ARDS were sepsis 50%, pneumonia 30%, aspiration pneumonia 20%, and mortality rate based on the etiology of ARDS was sepsis 50%, pneumonia 67%(p<0.01 vs sepsis), aspiration pneumonia 38%. Overall mortality rate was 60%. In 28 day-nonsurvivors, leading cause of death was severe sepsis(42.9%) followed by MOF(28.6%), respiratory failure(19.1 %), and others(9.5%). There were no differences in variables of age, sex, APACHE II score, HS, and numbers of organ dysfunction at day 1 of ARDS between 28-days survivor and nonsurvivors. In view of categorized variables of age(>70), APACHE II score(>26), HS(<150) at day 1 of ARDS, there were significant differences between 28-days survivor and nonsurvivors(p<0.05). After day 1 of ARDS, the survivors have improved their APACHE II score, HS, numbers of organ dysfunction over the first 3d to 7d, but nonsurvivors did not improve over a seven-day course. There were significant differences in APACHE II score and numbers of organ dysfunction of day 3, 7 of ARDS, and HS of day 7 of ARDS between survivors and nonsurvivors(p<0.05). Fatality rate of ARDS has been declined from 68% to less than 40% between 1995 and 1998. There were no differences in APACHE II score, HS, numbers of organ dysfunction, old age at presentation of ARDS. In last years, mean PEEP level was significantly higher and mean tidal volume was significantly lower than previous years during seven days of ARDS(p<0.01). Conclusions : Improvement of HS, APACHE II score, organ dysfunction over the first 3d to 7d is associated with increased survival Decline in ARDS fatality rates between 1995 and 1998 seems that this trend must be attributed to improved supportive therapy including at least high PEEP instead of conventional-least PEEP approach in ventilator management of acute respiratory distress syndrome.