OBJECTIVE: The perfusion index (PI) derived from plethysmographic signals provides a noninvasive indication of peripheral perfusion. This study aimed to investigate changes in PI and other hemodynamic variables in pigs subjected to endotoxemia. DESIGN: Prospective experimental study. SETTING: University teaching hospital. ANIMALS: Twelve healthy pigs weighing a mean (± standard deviation [SD]) of 31.7 ± 2.0 kg. INTERVENTIONS: Pigs were divided into control and endotoxin groups (n = 6 each). Endotoxemia was induced by IV infusion of lipopolysaccharide. Heart rate, mean arterial pressure, cardiac index (CI), central venous pressure, systemic vascular resistance index (SVRI), extravascular lung water index (ELWI), Global end-diastolic volume (GEDV) index, and pulmonary permeability index were measured using a transpulmonary thermodilution monitor in all pigs. PI was measured using a pulse oximeter probe attached to the tail. Pao2 , Paco2 , and plasma lactate concentration were measured by blood gas analysis. Measurements were taken at baseline (T0 ). Saline or lipopolysaccharide was then administered for 30 min to all pigs (control or endotoxemia group, respectively), and each parameter was measured every 30 min up to 270 min. Data were analyzed by analysis of variance and Student's t-tests. MEASUREMENTS AND MAIN RESULTS: There were no significant changes in any variables in the control group, but CI, SVRI, PI, ELWI, blood lactate concentration, and Pao2 changed significantly from baseline in the endotoxin group (P < 0.001, P = 0.0048, P < 0.001, P = 0.0064, P < 0.001, and P = 0.0220, respectively). In the endotoxin group, mean (± SD) %PI increased from T0 to 154 ± 34% at T60 (P = .001) and 135 ± 50% at T90 (P =0 .004), which mirrored significant changes in %CI and %SVRI. CONCLUSION: The PI may be useful to detect changes in CI and SVRI.