BACKGROUND Fournier's gangrene (FG) is a fulminant and fatal infection of the genitalia. However, the clinical course is unpredictable. This study retrospectively analyzed the possible prognostic factors of FG. METHODS Data obtained from 57 patients treated for FG from January 1985 through December 1996 were retrospectively analyzed. Possible prognostic factors including age, diagnostic delay, hospital stay, underlying diseases, clinical symptoms, origins, extents, bacteriologic findings, diverting colostomy and mortality rate were all considered in the analysis. RESULTS Patients with extensive or localized FG had mortality rates of 31.3% and 16.0%, respectively (p = 0.227). The mortality rates of patients with FG of anorectal, urogenital and non-specific origin were 30.3%, 0% and 40.0%, respectively (p = 0.712). The mortality rates of patients with FG of anorectal origin who received primary or secondary diverting colostomy were 16.7% and 40.0%, respectively. However, the mortality rate of patients with FG of anorectal origin who did not undergo diversion was 29.4%. The mortality rate of patients with FG presenting with septic shock at emergency was 53.8% as compared with 0% in those without septic shock (p < 0.001). CONCLUSIONS Fournier's gangrene is a rapidly progressive and life threatening infection of the genitalia. Age, underlying diseases, origin, extent and fecal diversion can not be regarded as prognostic factors of FG. Early primary diverting colostomy may reduce the mortality rate in those with severe infection of anorectal origin. Presence of septic shock in those with FG is the most important and the only factor related to death.