Abstract: When peanut gynophores were grown in vitro on MS medium, all gynophore tips planted at different angles showed gravitropic curvature at 6 h of culture, except for the gynophore with tip pointing downward. The change of endogenous hormones in peanut gynophores planted with tip pointing upward or downward morphologically in vitro was investigated by high performance liquid chromatography (HPLC). The results showed that the contents of IAA, GA3 and CTK decreased gradually in gynophores planted with tip pointing downward. IAA showed little change at all stages, and the contents of GA3 and CTK increased significantly in gynophores planted with tip pointing upward. On the contrary, the content of ABA increased gradually in gynophores planted with tip pointing downward, but decreased in the upward gynophores. The results indicated that these endogenous hormones might play an important role in gravitropic curvature of peanut gynorphores.