To examine the effectiveness of hyperbaric oxygen (HBO) therapy in the treatment of major truncal necrotizing infections, a retrospective (1980 to 1992) analysis of the medical records of 30 patients treated with HBO therapy and 24 patients treated without HBO therapy was undertaken. The two groups were similar; however, there was a selection bias towards more frequent clostridial infections in a younger population in the HBO group. There was no difference in length of hospital stay, intensive care unit (ICU) stay, or duration of antibiotic therapy between groups. The mortality rates were 9/30 (30%) in the HBO group versus 10/24 (42%) (nonsignificant difference) in the non-HBO group. The total number of operations was greater in the HBO-treated group. This study failed to show that the use of HBO in the treatment of major truncal necrotizing infections statistically reduced mortality or the number of débridements. We believe, however, that the apparent selection bias and the trend towards increased survival in the HBO-treated group (12%) justifies the continued use of and research with HBO therapy.