Abstract: Changes in levels of growth regulating substances during fruit development and maturation and the effects of abscisic acid application on ripening of apricot fruits were investigated. The results showed that the levels of growth promoting substances were high, but started to decrease rapidly just before the end of stage Ⅱ and continued throughout stage Ⅲ. The promoting substances almost disappeared in fully ripe fruits. The ABA-like inhibiting substances first appeared during the end of stage Ⅱ, increased significantly in stage Ⅲ, and reached a maximum level in fully ripe fruits. Exogenous ABA application enhanced fruit respiration rate and accelerated the ripening process when applied to preclimacteric fruits but inhibited these processes when applied to post-climacteric fruits. The above results suggested that the ABA may play an important role in apricot fruit ripening. The interrelationship of ABA, ethylene, and fruit ripening was discussed.