Abstract: Because explants of Momordica charantia were apt to form callus rather than adventitious buds during in vitro culture, we studied the contents of endogenous hormones in explants at different developing stages to explore the relation between adventitious bud differentiation and endogenous hormones and factors that limit the formation of adventitious buds. Use of enzymelinked immunosorbent assay (ELISA) revealed that (1) explants had higher content of indole-3-acetic acid (IAA) and lower content of iPAs, which resulted in difficulty in adventitious bud formation; (2) the differentiation of adventitious buds was tightly related with the ratio of IAA to iPAs; and (3)during in vitro culture, adventitious bud differentiation was promoted with a suitable level of cytokinin (such as Zeatin) and subculture in time.