This study was carried out to investigate the effect of Dormex sprayed at different concentrations and dates on bud behaviour, vegetative growth and yield of Superior grapevines. Three concentrations of Dormex were weekly sprayed: (0, 3 or 5%) at six dates: December 15‘“, December 22'“, December 29'“, January 5'“. January 12mand January 19'". it was evident from the results of the investigation that the best effective concentration of Dormex was 5%. The early Dormex application date (December 15"1 or December 22") gave too early bud burst with irregular and low percentage of bud break and conse uently the yield was very low. Moreover, the late Dormex application date (January 12 or January 19‘") greatly increased percentage of bud burst and bud fertility coefficient as a result of which average number of bunches and yield per vine were obviously increased. . The medium Dormex application date (December 29‘“ or January 5"") was recommended to achieve an early. uniform and high percentage of bud burst. in addition to, realizing reliable vegetative growth, and good yield with high bunch quality.