Chinese herbal formula bu zhong yi qi tang stablises male fertility Chinese herbal medicine, Bu Zhong Yi Qi Tang (Hochuekkito) is widely used for male infertility in Japan. There have been many reports concerning its clinical usefulness but very few reports of in vitro experiments studying the mechanism of its effects. In addition to stimulating germ cells, we analyzed its direct effects on sperm using computer assisted semen analyzer (CASA). Motile sperm were prepared using swim up technique from semen collected from ten healthy volunteers. Sperm movements (motility, velocity, linearity) were analyzed by CASA after adding either serum containing anti-sperm antibody (ASA) or normal serum with or without Bu Zhong Yi Qi Tang. Two hours after adding serum with ASA, the decrease of sperm motility was significantly reduced from 25.1% (92.8% -->67.7%) to 12.5% (92.9% -->80.6%) by adding Bu Zhong Yi Qi Tang. No significant difference in velocity and linearity was observed between two groups. By adding normal serum, any of three parameters differed significantly with or without Bu Zhong Yi Qi Tang. Protective effects of Bu Zhong Yi Qi Tang on sperm were suggested. Although normal sperm with ASA was used in this report, since the sperm of infertile patients are said to be more fragile, this results imply that direct protective effect is one of the mechanism of Bu Zhong Yi Qi Tang for male infertility. Reference Yamanaka, et al. (1998) Direct effects of Chinese herbal medicine "hachuekkito" on sperm movement. Nippon Hinyokika Gakkai Zasshi, 89(7):641-6 Jul (ISSN: 0021-5287).