The purpose of the present study was to determine if gender differences exist in the maximal accumulated oxygen deficit (MAOD) or in the blood lactate (Lac-) and catecholamine responses to the MAOD test (120% peak oxygen uptake to exhaustion). The MAOD for cycling was measured in ten untrained male and ten untrained female subjects using the method described by Medb蠥t?al. (Anaerobic capacity determined by maximal accumulated oxygen deficit. J Appl Physiol 64: 50-60, 1988). Blood Lac- and catecholamine concentrations were measured at rest, exhaustion and for 30?min following the MAOD test. Dual-energy X-ray absorptiometry was used to measure lean body mass (LBM) and to estimate the active muscle mass (AMM) for cycling. Males achieved a significantly higher MAOD than females following correction for AMM [126.3 (5.6) versus 108.3 (6.1)?ml?翫g AMM-1, P=0.04]. The peak blood lactate concentration ([Lac-]) in males [13.6 (0.9)?mmol?翬-1] was significantly higher than in females [10.0 (1.0)?mmol?翬-1]. Males obtained a 68% higher peak epinephrine concentration ([Epi]) than females, but the difference was not significant [1268 (188)?pg?翭l-1 versus 755 (179)?pg?翭l-1, P=0.066]. However, plasma [Epi] was significantly higher for males than females at 1?min [824 (116) versus 489 (116)?pg?翭l-1, P=0.036] and 3?min [330 (52) versus 179 (42)?pg?翭l-1, P=0.039] into the recovery period. No gender-dependent differences in the norepinephrine concentration were observed at any time. Peak [Lac-] was significantly correlated with MAOD (ml?翫g AMM-1) in females (r=0.75), but not in males (r=0.09). The peak plasma [Epi] was not significantly correlated with MAOD (ml?翫g AMM-1) or peak [Lac-] in either group. These findings suggest that there are gender-dependent differences in MAOD even when expressed relative to the AMM for cycling. The higher blood [Lac-] in males compared to females obtained after supramaximal exercise was not caused by enhanced secretion of Epi. The greater MAOD in untrained males was not caused by a greater ability to produce Lac- or by enhanced secretion of Epi.