It had been found that Yang-restoring herb medicines Radix Aconiti Praeparata (AP), Cortex Cinamomi(CC), Herba Cistanchis(HC) and Epimedium brevicorum (EB) reduced the cold-resistant potential of normal mice and disturbed the balance of thyroid hormones in normal rats. The aim of this study was to further investigate the effects of these four herb medicines on the levels of plasma corticosterone (B), testosterone (T) and triiodothyronine (T3) in rats by administering herbs together (mixed group) or individually. It was shown that all four Yang-restoring herbs tended to raise plasma B level and it was significant in HC, EB and mixed groups, especially in HC administered rats (P less than 0.001). Rise of plasma T level was seen in CC and mixed groups. All four herbs could decrease plasma T3 level and it was significant in AP, CC and mixed groups, particularly evident in AP administered rats (P less than 0.001). This may be one of the adaptating-protecting mechanisms of normal organism against the toxicity of AP. Combination of the four herb medicines did not result in the cumulation of effects of the given medicines, however, this did reflect the average effect of these four herbs, which showed a restraining and harmonious relationship in a Chinese medical prescription.