Most treatment with hyperbaric oxygen (HBO) in plastic surgery is for wounds, burns, crush injuries, and infections. We aimed to find out if HBO increases the survival of composite grafts in rats. Twenty Sprague-Dawley rats were randomly assigned to two equal groups (treatment and control). A template 30 x 30 mm was placed on the skin and a composite graft taken from the upper back was harvested and then resutured to the fascia in situ. The treated group was placed in a hyperbaric chamber set at 202 kPa and 100% oxygen for 90 minutes daily for two weeks. Control animals were given no treatment. After death the mean surviving internal surface area of the graft was 372.5 (117.9) mm2 in the control group and 561.3 (85.7) mm2 in the experimental group (p=0.001). Treatment with HBO improved the surviving area of composite grafts in rats, and the beneficial effect was prominent only on the inner surface of the graft.