A new model of in vitro cardioplegic oxygenation was evaluated by placing Ringer's infusion bags in a pressure resistant barrel filled with pure oxygen maintaining 380mmHg. In this hyperbaric environment, oxygen gradually diffused directly through the wall of the infusion bag reaching a concentration exceeding four volumes percent after 96 hours. Decay in oxygen content was less than 1.5% after one week refrigerated at 4°C. In conclusion, the method described above offers an alternative approach to cardioplegic oxygenation, with the advantage of being safe, simple and without any extra expenditure.