Root rot disease was studied in several olive nurseries and orchards in Ismailia, Behera, Giza and Fayoum governorate. Observed disease symptoms were leaves internal rolling, partial wilt, yellowing or browning of leaves, drying of branches and leaves, twig dieback and severe root rot. Fusarium konzum was the most pathogenic fungus, followed by F. solani. All evaluated olive cultivars were susceptible to the tested fungi however, cultivar Picual was the most susceptible while Koratina was the least one. The infection of Picual, Maraki, Kroneiki and Koratina with F. konzum increased the total sugars and decreased total sugar contents and non-reducing sugars in Toffahi. Also, the infection of olive transplants of cultivar Kroneiki with F. konzum or F. solani increased the total phenols however, decreased the total phenols in cvs. Toffahi, Maraki and Koratina. Oleuropin, Pyrogallol and E-vanillic increased in infected olive transplants of cv. Picual by F. konzum or F. solani. The highest amounts of flavonoids in both of healthy and infected tissues of cvs. Koratina and Picual were Luteo.6-arbinose8-glucose and Apig. 6-glucose8-rhamnose. The oxidative enzymes peroxidase, poly-phenoloxidase and catalase recorded an increment in infected tissues of the tested olive cultivars compared to the control and catalase was the highest activity however, poly-phenoloxidase was the least one.