Alternate bearing is one of the most important phenomena in the olive trees. A study was conducted during 2002 - 2003 at the Agricultural Research Center in Homs on two olive varieties (Sorani and Daebli) to assess the effect of flower and fruit thinning at different time intervals on flowering differentiatian, percentage of vegetative buds, length of branch, length of the internodes and total number of buds. The results showed that: - flower thinning and treatment with Gibberellic acid (GA3) during the maximum flowering did not influence the percentage of buds, while flower thinning during different periods folowed by treatment with Gibberellic acid during the fruit setting phase, endocarp sclerification had significantly decreased the percentage of flower buds for Sorani variety in 2002 and 2003 during the fruit setting phase and two weeks later. In Daebli variety this treatment decreased the percentage of flower buds during fruit setting, two weeks later, and after four weeks from fruit setting whereas, the treatment had not effect in both the varieties during endocap sclerification stage.