The authors collected epidemiological and clinical informations on 1,307 CO patients from the questionairefilled by attendants of patients and from the clinical records kept in the hospital. All patients were treated by hyperbaric oxygenation at the Hyperbaric Chamber Unit of Seoul National University Hospital during 5 years, from January, 1969 to December, 1973. The following findings were obtained. 1. Female showed higher incidence rate than male. The highest incidence rate was observed in the age group of 15-29 years in both sex. 2. The most important variable influencing the recovery of the patients was the starting time of treatment. It was evident that earlier the starting time, shorter the recovery time. 3. Duration of admission was within 5 days in 57.1 percent of the admitted cases and 76.1 percent of them was discharged within 8 days. 4. As the complications, pulmonary edema, bronchopneumonia and trophic changes were observed. Also the neurological disorders were found. 5. The fatality rate followed by the hyperbaric oxygenation was 1.07 percent.