Changes in blood lactic acid density after 10 minutes of 80% VO₂max. bicycle exercise due to bathing in CO₂ water obtained from a newly developed CO₂ water generator (MCH-C80: Maeda Iron Works Co., Ltd.) were compared with changes due to bathing in plain water. The blood lactic acid density increased from 1.6mmol/l to 9.3mmol/l due to the exercise load, but decreased to 3.3mmol/l after 10 minutes of CO₂ water bathing at 38°C and further decreased to 1.9mmol/l after 30 minutes. In the group bathing in plain water, blood lactic acid density decreased to 4.0mmol/l immediately after bathing and to 2.3mmol/l after 30 minutes. The difference in results between the CO₂ water bathing group and plain water groups was significant (p<0.05). No bad effects of CO₂ water bathing were observed. Thus, CO₂ water obtained from this CO₂ water obtained from this CO₂ water generator is useful for enhancing the effect of bathing on recovery from fatigue.