In an experimental study standardized third-degree burns were caused in guinea pigs. The animals were treated intermittently with hyperbaric oxygen for a period of five days starting immediately after injury. The healing process was recorded at frequent intervals using a photographic technique and planimetric determinations. In addition, the wounds were excised at predetermined intervals for the purpose of histological examination. Untreated animals demonstrated a considerable increase in wound area as compared to the initial lesion, while there was a tendency to reduced wound area in the treated animals. Histological studies revealed considerably less subcutaneous edema in tissue samples obtained from the treated animals than in specimens from the control group. The effect of hyperbaric oxygen on fresh burns is discussed on the basis of the experimental findings.