Gender differences in maximal accumulated oxygen deficit (MAOD) were examined before and after 4 and 8 wk of high-intensity interval training. Untrained men (n=7) and women (n=7) cycled at 120% of pre-training peak oxygen uptake (VO₂) to exhaustion (MAOD test) pre-, mid-, and post-training. A post-training timed test was also completed at the MAOD test power output and was stopped at the time to exhaustion (TE) achieved during the pre-training MAOD test. The 14.3±5.2% increase in MAOD observed in males after 4 wk of training was not different from the 14.0±3.0% increase seen in females (p>0.05). MAOD increased by a further 6.6±1.9% in males and this change was not different from the additional 5.1±2.3% increase observed in females after an additional 4 wk of training. Peak VO₂ measured during incremental cycling, increased significantly (p<0.01) in male but not in female subjects after 8 wk of training. Moreover, the AO₂ uptake was higher in men during the post-training timed test compared to the pre-training MAOD test (p<0.01). In contrast, the AO₂ uptake was unchanged in female subjects. The increase in MAOD with training was not different between men and women suggesting an enhanced ability to produce ATP anaerobically in both groups. However, the increase in VO₂peak and AO₂ uptake obtained in male subjects following training indicates improved oxidative metabolism in men but not in women. We conclude that there are basic gender differences that may predispose males and females to specific metabolic adaptations following a period of intense interval training.