To elucidate the mechanisms underlying fruit growth and development of Chinese gooseberry (Actinidia chinensis Planch.), the effects of four growth regulators on fruit growth and development were examined. In addition, the mechanism of KT-30 action on fruit growth and development and the methods to improve the undesirable qualities found in the KT-30-promoted large fruits were studied. The results obtained were as follows: 1. In the treatments of fruits with four growth regulators, KT-30, GA_3, IAA, and ABA, carried out in stage Ⅱ of the fruit growth cycle (12 weeks after anthesis), no effects were found on the fruit growth and bevelopment. 2. Girding of the base of bearing branches increased fruit weight of 17g in the KT-30 treated fruits and of 16g in the untreated fruits. 3. The effects of KT-30 on the enlargement of fruit size varied with the treatment time and concentrations. KT-30 applied to buds one to three weeks before anthesis greatly promoted enlargement of the ovaries but did not promote enlargement of the ovaries after pollination. KT-30 applied to buds one day before anthesis promoted enlargement of the fruits moderately, while treatments of fruits two to four weeks after anthesis promoted it greatly. 4. The firmness of KT-30-treated fruits decreased as the concentration of KT-30 increased and as the size of the KT-30-treated fruit increased. The percentage of fruits with rib, which appeared after anthesis, increased as the concentration of KT-30 increased. It becomes clear that the development of the rib is due to ununiformity of the KT-30 solution on the fruit surface. 5. Application of a solution of 5 ppm KT-30 mixed with 200 ppm GA_3 to the fruits 2 weeks after anthesis resulted in the increase of the fruit firmness, dicrease of the percentage of fruits with rib and increase of fruit size.