Prognosis of iatrogenic air embolism is various according to previous studies. The purpose of this study was to determine the risks factors associated with the prognosis of iatrogenic air embolism. We conducted a retrospective analysis of 113 patients treated with HBO therapy in our hyperbaric center from 1979 to 1993. Initial symptomatology consisted in neurological disorders (71% of cases), respiratory disorders (43% of cases) and hemodynamic disorders (33% of cases). When neurological disorders were observed, HBO therapy included immediate compression to 6 atm abs for 10 to 15 mn with air followed by decompression to 2 atm abs where the patients received 100% oxygen during 1 hour. When no neurological disorders was observed, HBO therapy consisted in an oxygenation for 1 h, 2 atm abs, FiO2 = 1. Overall outcome was: recovery: 69 per cent of cases, sequelae: 26 per cent of cases, death: 5 per cent of cases. Prognosis was very different according to etiologies and existence of neurological disorders. Venous emboli had a better improvement than arterial emboli. In conclusion, patterns of air embolism can be divided clinically into two major categories, cerebral and pulmonary air embolism, which should be individualised in clinical studies. The studies must also individualised etiologies.