The purpose of this study was to determine, using the isolated liver perfusion technique, if the limiting factor for hepatic gluconeogenesis (GNG) from lactate was precursor delivery or oxygen availability during reduced flow rates of 0.85 or 0.60 ml/min x g liver^-1. Following a 24 hour fast, three different experimental protocols were employed. Protocol 1 examined the impact upon GNG when reservoir lactate concentration was maintained, but oxygen delivery was elevated via increases in hematocrit (Hct). Elevating the Hct from 22.5 ± 0.8% to 30.9 ± 0.4% at a blood flow of 0.89 ± 0.01 ml/min x g liver^-1 increased the oxygen consumption (VO₂), but did not augment GNG. Similarly, when the Hct was elevated from 22.5 ± 0.8% to 41.5 ± 0.7% at 0.59 ± 0.04 ml/min x g liver^-1 VO₂ was increased, but GNG was unaffected. Protocol 2 examined the impact upon GNG when Hct was maintained, but precursor delivery was elevated via increases in reservoir lactate concentration ([LA]). Specifically, elevating the [LA] from 2.31 ± 0.07 to 3.61 ± 0.33 mM at a flow rate of 0.82 ± 0.04 ml/min x g liver^-1 significantly increased GNG. Similarly, elevating the [LA] from 2.31 ± 0.07 to 4.24 ± 0.37 mM at a flow rate of 0.58 ± 0.02 ml/min x g liver^-1 increased the GNG. Finally, we examined the impact of increasing both the oxygen and lactate delivery (Protocol 3). Again, VO₂ was elevated with increased oxygen delivery, but GNG was not augmented beyond that observed with elevations in lactate delivery alone, i.e., Protocol 2. The results indicate that during decrements in blood flow, GNG is limited primarily by precursor delivery, not oxygen availability.