Increase in fat mobilization by capsaicin(CAP) was investigated in high-fat-fed mice using an adjustable current water pool. Male ICR 7-wk-old mice were fed a high fat diet [50% total energy content in the diet(E%) fat, 20 E% protein, 30E% carbohydrate] for 2 wk and one group (HCAP) was orally administered CAP at 2 h before swimming. After being accustomed to swimming , the mice were subjected to forced swimming every 2d in the current water pol and the total swimming period until exhaustion was measured . The total swimming period was used as index of swimming capacity. Swimming time to exhaustion of treated mice was significantly longer than that of the high-fat-fed control group (100.2$pm$10.6 vs. 58.0$pm$8.5min, P<0.01) after 2wk of training. The concentration of serum-free fatty scids gradually increased up to 2 h in CAP -administered mice. The perirenal adipose tissue weight of CAP -administered mice (HCAP) before swimming was lower than that of the high-fat-fed mice adminstered placebo solution (HP) which had not ingested CAP during the 2 wk. These results suggest that the increase of swimming capacity of CAP-administered high-fat-fed mice was due to an increase of fat mobilization that was induced by CAP.