The gonadotropin-releasing hormone (GnRH) analogue (Leuplin/^®1.0mg/kg, s. c.) induced not only a decrease in the serum concentration of testosterone but also potentiation of calcitonin gene-related peptide (CGRP: 10μg/kg, i. v.)-induced elevation of skin temperature in male rats. Keishi-bukuryo-gan (1, 000mg/kg, p. o.) and 17β-estradiol (0.010mg/kg, s. c.) significantly inhibited the elevation of skin temperature as well as teststerone (1.0mg/kg, s. c.) replacement. However, Keishi-bukuryo-gan and 17β-estradiol did not affect the low concentration of serum testosterone, although the hormone replacement of testosterone restored the plasma level. These results suggest that Keishi-bukuryo-gan, which does not have testosterone activity to serum, may be useful for the treatment of hot flushes due to testosterone deficiency after GnRH therapy in men with prostatic carcinoma, as well as 17β-estradiol.