An experimental multimicrobial gas gangrene rat model was developed and the therapeutic effect of surgery was compared to the combined effect of surgery and hyperbaric oxygen (HBO). The infection was caused by an intramuscular injection of a mixture of bacteria including Clostridium perfringens, Bacteroides fragilis, Escherichia coli and Streptococcus faecalis. The mortality, morbidity and wound healing were assessed during a follow-up of 2 weeks. The mortality of the control rats was 60%, with rats treated with surgery alone 35 % and the combined treatment group 20% (NS). In the combined treatment group, 84.4% of the survivors healed completely; the corresponding figure in the surgery group was 15.4% (p < 0.001). In experimental multimicrobial gas gangrene the addition of HBO to surgery reduces morbidity and improves wound healing but does not reduce mortality statistically significantly.