OBJECTIVE : To compare the lactate concentrations obtained from venous to those obtained from arterial blood in predicting hospital mortality of patients with sepsis and septic shock. To also assess lactate clearance as predictor for mortality. METHODS : 100 patients with septic shock were prospectively enrolled. Serum was sampled at baseline and after 6 h of resuscitation from arterial and venous lines. Demographic, severity indices, hemodynamic measures as well as lactate clearance levels were noted. Data were analyzed for bias and precision. RESULTS : There was correlation between venous and arterial lactate concentrations at the baseline (R = 0.68) and at the 6-hour time point (R = 0.95). Venous concentrations were consistently higher than those obtained from an arterial access by 0.684 mg/dL. Further, arterial lactate level > 3.2 mmol/L and clearance of <20% were considered the cutoff for the mortality risk. While only 8% of the patients with no risk died, all 20 patients who had lactate level > 3.2 mmol/L and clearance of <20% died within the hospital. CONCLUSIONS : Our data suggests a strong correlation between arterial and peripheral venous the lactate levels and in the initial phase of resuscitation in septic shock patients we can use venous lactate level as biomarker instead of arterial lactate level. The study also showed that combining lactate levels and its clearance is a reliable predictor of mortality in sepsis.