To clarify the effects of exercise on the anti-tumor activity at in vivo and in vitro, We performed a well designed experiment with animal model, 8-week-old ICR male mice were divided in two group. 1) control group(not-exercised). 2) exercise group(exercised 20∼30m/min, inclination 8%) 5times per week, for 12 weeks, To investigate the anti-tumor effect at in vivo, at 12 weeks from the beginning of exercise, sarcoma-180 cells were inoculated into peritoneal cavity in control and exercise groups, and thereafter survival time was checked, The NK cell and LAK cell activity at in vivo were checked at the end of exercise and rest time of 48hrs. The mice if exercised groups showed higher level of NK cell and LAK cell activity than the control group. On the other hand, There was nor difference in anti-tumor effect at in vivo between control and exercise group. These results, suggest that exercise modulate the NK and LAK cell at activity but not effect in vivo anti-tumor effect.