The purpose of this study was to examine the effect of short-term training on maximum oxygen uptake (VO2 max) and two different measures of endurance performance. Endurance was determined for 15 female subjects (7 training, 8 control) as (1) exercise time to exhaustion at 80% VO2 max (T80%) and (2) the highest relative exercise intensity tolerable during a 30-minute test (T30 min), before and after a 6-week training period. In addition, VO2 max and the work rate equivalent to a blood lactate concentration of 4 mmol.l-1 (OBLA) were determined. Maximum oxygen uptake increased by 24% (p less than 0.01) for the training group (TG) and 7% (p less than 0.01) for the control group (CG). Cumulative average work rate (CAWR) during T30 min increased by 25% for the TG while there was no change for the CG. No significant difference was found pre- and post-training in the %VO2 max (estimated from CAWR) at which the TG and CG performed T30 min. Exercise time to exhaustion on T80% increased by 347% (p less than 0.01) and 16% (NS) for the TG and the CG respectively. Good correlations were found between VO2 max and CAWR (W) (pre-training r = 0.84; post-training r = 0.83), OBLA (W) and CAWR (W) (pre-training r = 0.89; post-training r = 0.88) and change in endurance time and the change in submaximal blood lactate concentration (r = 0.70, p less than 0.01). The results of this study suggest that the ability to sustain a high relative exercise intensity is not enhanced following short-term training.