PURPOSE: Hypocitrullinemia has been suggested to be a prognostic factor for patients in intensive care. The aim of this ancillary study of the Corticosteroids and Intensive Insulin Therapy for Septic Shock prospective study was to investigate plasma l-citrulline concentrations and its relationship with inflammation and digestive bacterial translocation in patients with septic shock multiorgan failure and without primary intestinal disease or chronic renal failure. METHODS: Sixteen adult patients were selected. They were studied on day (D) 0 at hours (H) 0, 6, 12, 18, and 24 and on D4 (H96). Selected plasma amino acids and proteins, proinflammatory (tumor necrosis factor α [TNF-α]) and anti-inflammatory (interleukin [IL] 10) cytokine concentrations, and bacterial translocation were measured. RESULTS: Eight D14 survivors and 8 D14 nonsurvivors patients were studied. Citrulline was decreased on D0 (H0: 29 ± 10 vs nadir: 18 ± 6 μmol/L; P < .05). The citrulline nadir was lower (P < .01) in patients with digestive bacterial translocation than that in those without. Mean citrulline concentrations at H0 to H96 were not significantly different between survivors and nonsurvivors. In both groups, citrulline was significantly inversely correlated with C-reactive protein (r(2) = 0.10, P < .01) on D0. No significant correlations were found between citrulline and albumin, transthyretin, TNF-α, IL-10, or TNF-α/IL-10 ratio. CONCLUSIONS: At the onset of septic shock, plasma citrulline decreases and varies inversely with C-reactive protein and is lower when digestive bacterial translocation occurs. This finding could reflect an early acute intestinal dysfunction, but measurement of citrulline concentration does not appear to be able to predict the patients' mortality.