BACKGROUND: In animal studies, gender differences were related to hormonal and immunologic changes that were associated with an increased susceptibility to sepsis in males. OBJECTIVE: In a prospective study, gender differences in patients with surgical sepsis were evaluated in terms of survival, sex hormones, and proinflammatory as well as anti-inflammatory mediators. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: Fifty-two patients (19 women and 33 men) with surgical sepsis. MEASUREMENTS AND MAIN RESULTS: In a prospective study, tumor necrosis factor alpha and interleukin 6 bioactivity and plasma levels of interleukin 10 (using enzyme-linked immunosorbent assay), total testosterone, and 17-beta estradiol (using radioimmunoassay) were determined on days 1, 3, 5, 7, 10, and 14 after diagnosis of sepsis. There were no differences in characteristics of patients in age (mean age, 55.4 years for women and 53.1 years for men) or cause and severity of sepsis (Acute Physiology and Chronic Health Evaluation II score, 17.3 for women and 18.5 for men; multiple organ dysfunction score, 9.9 vs 10.8, respectively). Although no difference could be found in the multiple organ dysfunction score from day 1 to day 28, the prognosis of sepsis was significantly different in women compared with men. Hospital-mortality rate was 70% (23 of 33 patients) in male and 26% (5 of 19) in female patients (P<.008, log-rank test). Bioactivity of tumor necrosis factor continuously increased in men after diagnosis of sepsis, with significantly elevated levels on day 10 (P<.05, Mann-Whitney U test with Bonferroni correction), whereas no difference was found for interleukin 6 bioactivity. Women displayed enhanced interleukin 10 levels compared with men from day 1 to day 10 that reached a significant difference on days 3 and 5 (P<.05). Total testosterone levels were below the normal range for men, and estradiol levels were initially increased in both men and postmenopausal women, with higher levels for women. CONCLUSIONS: In this prospective study, gender differences were confirmed in human sepsis, with a significantly better prognosis for women, which may be related to increased levels of anti-inflammatory mediators. The hypothetical different ratio of proinflammatory and anti-inflammatory mediators may be important for further therapeutic interventions in sepsis.