BACKGROUND: ALI (Acute Lung Injury) and ARDS (Acute Respiratory distress Syndrome) which are related one or more risk factors (e.g. sepsis, aspiration, pneumonia, multiple trauma) show diffuse infiltrative pulmonary edema on chest X-ray and result in hypoxic state in spite of oxygen supply. Even though patients are managed intensively with mechanical ventilation, the mortality rate has been 50-60%. Therefore, early prediction of prognosis in such patients should be considered a high priority so that corrective measures or alternative support methods may be rapidly instituted. METHODS: We studied various prognostic factors prospectively in 34 patients with acute respiration failure who survived more than 7 days after receiving mechanical ventilation continuously in the intensive care unit of Chonnam National University Hospital. We measured or calculated dynamic and static compliances, PaO2/FiO2, PaO2/PAO2, A-a DO2 and APACHE iii score and compared these daily variables between the survivor and non-survivor groups. RESULTS: The non-survivor group was mostly old-aged while sex ratio duration of mechanical ventilation didn't show any significant difference between these two groups. The static and dynamic compliances showed significantly higher values in the survivor group throughout 7 days ratio of PaO2/FiO2 and PaO2/PAO2 tended to the higher in the survivor group and A-a DO2 was higher in non-survivor group. APACHE iii score from the 3rd day after mechanical ventilation was significantly lower in the survivor group and there was a tendency of gradual decrease in the survivor group but gradual increase in non-survivor group. CONCLUSIONS: Age, dynamic and static compliances and APACHE iii score showed significant differences between the survivor and non-survivor groups. Each value of above factors showed the characteristic changing patterns throughout the first 7 days after mechanical ventilation. With these results, these parameters suggest to be helpful in the early prediction of outcome in the mechanically ventilation patients with acute respiratory failure.