This study was undertaken to determine the relationship of arterial and venous base deficit (BD) to lactate levels and SvO2 in shock and resuscitation with the hypothesis that BD is an equally good indicator of the physiologic changes while being more readily accessible. Fifteen mature swine were bled serially of 25% and 40% of their calculated blood volumes, then resuscitated with lactated Ringer's and blood. Serial hemodynamic and metabolic measurements were made. The BD correlated significantly with lactate levels at all increments of shock and resuscitation. Linear regression analysis demonstrated strong associations (p < 0.001) for arterial and venous BD (R = 0.808), for BD and lactate (R = -0.794), and BD and SvO2 (R = 0.538). The BD accurately reflected the hemodynamic and tissue perfusion changes associated with hemorrhagic shock and resuscitation. Base deficit is more readily available than lactate, and is therefore more useful as an index of shock and resuscitation. Venous BD correlates well with arterial BD and can be used when an arterial sample cannot be obtained. The SvO2 correlated well with acute volume changes but the addition of supplemental oxygen made it a less reliable indicator of hemorrhage and resuscitation.