Sixteen (16) C.O.L.D. patients with acute respiratory failure entered this preliminary study to evaluate the effects of almitrine bismesylate against placebo. Eight (8) patients received almitrine bismesylate and eight (8) patients received placebo. During the study, (11) patients were intubated and one (1) patient died because of bleeding peptic ulceration. A significant improvement in PaO2 values was noted in the patients given almitrine bismesylate as opposed to those given placebo. This improvement (p = 0.032) became evident on the 2nd day of treatment. The changes in PaO2 levels were not modified by intubation. A surprising evolution of PaCO2 was observed in those patients given almitrine bismesylate whether or not they had been intubated. No side effects were noted in the patients taking almitrine bismesylate during the first 4 days of the trial or during the following 6 days when patients continued to receive almitrine bismesylate.