The effect of oral creatine supplementation on aerobic and anaerobic performance was investigated in 16 elite male rowers during 7-day endurance training. Before and after the daily ingestion of 20 g creatine monohydrate for 5 days (Cr-Group, n=8) or placebo (Pl-Group, n=8), subjects performed two exercise tests on a rowing ergometer: (a) incremental exercise consisting of 3-min stage durations and increased by 50 W until volitional exhaustion; (b) an all-out anaerobic exercise performed against a constant load of 7 W/kg. Heart rate and blood lactate concentrations were determined during exercise and recovery. Maximal power output did not significantly differ after the treatment in either group. The mean individual lactate threshold rose significantly after Cr treatment from 314.3 +/- 5.0 W to 335.6 +/- 7.1 W (p<.01), as compared with 305.0 +/- 6.9 W and 308.9 +/- 5.9 W (ns), before and after placebo ingestion, respectively. During the anaerobic test, the athletes supplemented with creatine were able to continue rowing longer (mean increase, 12.1 +/- 4.5 s; p<.01) than Pl-Group (2.4 +/- 8.2 s; ns). No significant differences were found between groups in blood LA after the all-out exercise. The results indicate that in elite rowers, creatine supplementation improves endurance (expressed by the individual lactate threshold) and anaerobic performance, independent of the effect of intensive endurance training.