To evaluate the effect of hyperbaric oxygen therapy on chronic wound healing, 16 otherwise healthy patients who had nondiabetic, chronic leg ulcers with no large vessel disease were included in a double-blind study. Patients were grouped according to age and then randomly assigned to two groups breathing either air or oxygen at 2.5 atmospheres of absolute pressure for 90 minutes 5 days per week for a total of 30 treatments. The wound area was copied onto transparent film covering the wound and then measured using only one matching wound from each patient. The mean decrease of the wound areas at weeks 2, 4, and 6 in the oxygen group were 6 percent (SD +/- 14), 22 percent (SD +/- 13), and 35.7 percent (SD +/- 17), respectively, and in the air group, 2.8 percent (SD +/- 11), 3.7 percent (SD +/- 11), and 2.7 percent (SD +/- 11), respectively, giving a p value less than 0.05 at week 4, and a p value less than 0.001 at week 6 between the groups using the Mann-Whitney U test. These data indicate that hyperbaric oxygen therapy may be used as a valuable adjunct to conventional therapies when nondiabetic wounds do not heal.