OBJECTIVE AND DESIGN: To evaluate the association of pro-inflammatory mediators with organ dysfunction and adverse outcome in intra-abdominal sepsis patients. SUBJECTS: Twenty-one patients admitted to the Intensive Care Unit (ICU) were prospectively included in the study. Only patients with surgical diagnosis of intra-abdominal sepsis were enrolled. RESULTS: Tumor necrosis factor-alpha (TNFalpha) and interleukin (IL)-6 produced ex vivo were significantly lower in non-survivors on admission (p = 0.021) and day 2 (p = 0.013), respectively. Nitric oxide (NO( x )) levels were significantly higher in non-survivors from the onset of sepsis and until day 4 after diagnosis (p < 0.05). Circulating lymphocyte counts were lower in non-survivors after admission over time, but there was no association with impaired cytokine production in this group of patients during the entire follow-up. All non-survivors developed nosocomial pneumonia concomitantly with multiple organ dysfunction and septic shock. There was a significant correlation between nitric oxide (NO( x )) concentrations and the sequential organ failure assessment (SOFA) score at day 2 (r = 0.598, p = 0.009), and ICU stay (r = 0.605, p = 0.006). Continuously high NO( x ) levels correlated with organ failure. The pro-inflammatory mediators TNFalpha, IL-6 and NO( x ), and also the Simplified Acute Physiology Score II (SAPS-II), discriminate survivors from non-survivors. According to logistic regression models, although these parameters are independently associated with the outcome, they do not improve the predictive power of the SAPS-II score for mortality risk. CONCLUSIONS: Disturbances in inflammatory responses and increase in NO( x ) generation seem to characterize early intra-abdominal sepsis, in which immune suppression is associated with an increased susceptibility to nosocomial infections. Sequential NO( x ) determinations could be a useful approach for improving the management of patients with intra-abdominal sepsis.