Between 1971 and 1987, 32 patients with clostridial gas gangrene were treated in the Department of Surgery, University of Turku. A presumptive diagnosis of gas gangrene was made on the basis of the clinical appearance of the patient and a predominance of Gram positive rods on stain. Between 1973 and 1989, 11 patients with perineal necrotizing fasciitis (Fournier's gangrene) were treated. The diagnosis was based on fulminating progression of perineal gangrene and on the presence of multiple pathogenic organisms in the primary Gram stain or culture. All patients in both series underwent surgical debridement, antibiotic therapy, and intensive care. In addition, the patients were exposed to pure oxygen at 2.5 atmospheres absolute pressure (ATA) for 120 minutes. Three such treatments were given during the first 24 hours after admission after which the treatment was repeated twice daily. Seventeen patients with clostridial gas gangrene had diffusely spreading myonecrosis; 6 died. Fifteen patients developed clostridial cellulitis with toxicity; 3 died. Thus, the overall mortality in gas gangrene was 28%. All the 9 patients who died had been transferred from other hospitals in Finland and were moribund on arrival. The infection in 8 of these patients developed postoperatively. None of the patients with a posttraumatic infection died. Each of the patients with Fournier's gangrene had had nonspecific symptoms before the gangrene became evident. The infection originated from the anorectal area in 5 patients, 1 patient had sustained a scrotal trauma and in 5 patients the underlying condition was unknown. One patient died 2 days after admission. Six patients required a colostomy. To evaluate the therapeutic value of hyperbaric oxygen (HBO) treatment, two experimental models of clostridial gas gangrene, mono- and multimicrobial, were developed in rats. In the monomicrobial infection model, 10(7) colony forming units (cfu) of Clostridium perfringens were injected intramuscularly into the left hind limb of the rat. The mortality of untreated rats was 100%. The mortality of the rats treated with surgery alone was 38% compared to 13% when surgery was used in combination with HBO (p < 0.01; chi 2 test). In the group treated with HBO and surgery, 94% of the survivors healed completely and were able to walk normally, whereas the corresponding figure in the rats treated with surgery alone was 20% (p < 0.001; chi 2-test). In the multimicrobial gas gangrene model the infection was induced by an intramuscular injection of a mixture containing approximately 10(7) cfu of each of the following bacteria: Clostridium perfringens, Bacteroides fragilis, Escherichia coli and Streptococcus faecalis.(ABSTRACT TRUNCATED AT 400 WORDS)