The purpose of this study was to examine the influence of acute plasma volume expansion (APVE) on oxygen uptake (V_O2) kinetics, V_O2 peak and time to exhaustion during severe-intensity exercise. Eight recreationally-active males performed step cycle ergometer exercise tests at a work rate requiring 70% of the difference between the gas exchange threshold and V_O2 max on three occasions: twice as a control and once following intravenous infusion of a plasma volume expander (Gelofusine; 7 mL/kg body mass). Pulmonary gas exchange was measured breath-by-breath. APVE resulted in a significant reduction in hemoglobin concentration (pre: 16.0 ± 1.0 vs. post: 14.7 ± 0.8 g/dL; P<0.001) and hematocrit (pre: 44 ± 2 vs. post: 41 ± 3%; P<0.01). Despite this reduction in arterial O₂ content, APVE had no effect on V_O2 kinetics (Phase II time constant, CON: 33 ± 15 vs. APVE: 34 ± 12 s; P=0.74), and actually resulted in an increased V_O2 peak (CON: 3.90 ± 0.56 vs. APVE: 4.12 ± 0.55 L/min; P=0.006) and time to exhaustion (CON: 365 ± 58 vs. APVE: 424 ± 64 s; P=0.04). The maximum O₂ pulse was also enhanced by the treatment (CON: 21.3 ± 3.4 vs. APVE: 22.7 ± 3.4 mL/b; P=0.04). In conclusion, APVE does not alter V_O2 kinetics but enhances V_O2 peak and exercise tolerance during high-intensity cycle exercise in young recreationally-active subjects.