The use of grafting technology in vegetable crops, represents a significant component of the vegetable industries throughout the world. Most, if not all rootstocks and successful grafting combinations are selected on the basis of empirical testing. Obviously, there is a need for better understanding of the endogenous factors which control rootstock scion communication and processes which lead to the beneficial effects of grafting. The huge progress in understanding signaling processes and the involvement of phyto-hormones in all aspects of plant development and crop productivity may be utilized for more profound probing into rootstock-scion communication in grafted plants. This review summarizes some of the research results in four aspects of hormonal signaling in rootstock-scion interactions: (1) formation of the rootstock-scion union; (2) rootstock-scion communication; (3) improvement of grafting interactions by hormonal manipulations; (4) hormonal influence on growth, flowering, and fruit quality. (C) 2010 Elsevier B.V. All rights reserved.