Gibberellic acid did not affect ethylene production, whereas gibberellin biosynthesis inhibitors triggered ethylene production in dormant tubers. Gibberellic acid did not induce sprouting of dormant tubers, however, treatment of gibberellin biosynthesis retardants enhanced sprouting rates. Sprouting rate in ancymidol-treated tubers was highest among gibberellin biosynthesis retardants. Sprouting rate of tubers treated with ancymidol increased to 91.4~% . Batatasin-III content in GA3 treated tuber was increased in the highest concentration (30~mug~;I-1) . Tubers treated with mepiquat chloride, Batatasin-I was increased steadily, but contents of Batatasin-III and V showed dramatic decrease at the 1,000~mug~;I-1) concentration. This infers that gibberellin biosynthesis retardants play key roles in promoting breaking dormancy on dormant tubers of Chinese yam.