Abstract: Four algae strains: Dunaliella salina, Chlorella ellipsoidea, Scenedesmus acutus and Scenedesmus dimorphus were cultivated under stress condition, where carotenogenesis (reneged from 4.69 to 13.14 g 100 g-1 d.w) and tocopherols (1.23 to 3.75 g 100 g-1 d.w) accumulation are induced. The carotenoids have been analyzed by high performance liquid chromatography (HPLC) and were found to contain at least 14 different carotenoids. Of which, β-carotene (23.15 to 80.6%), canthaxathin (5.4-41.2%) and astataxanthin (10.2 -31.2%) were identified as major carotenoids. The lipophilic algae extracts (20 mg dose-1 every two days /mice) were administrated in continued dosages for 2 weeks to mice pretreated with 0.25% solution of benzo(a)pyrene kg-1 [B(a)P] in corn oil as a single dose. The lipophilic algae extracts (phycotene) were shown to significantly increased the activity of the cellular detoxifying enzyme glutathione S-transferase (GST) being about 2.88 - 6.29 times higher than that the untreated mice. The administration of algal extracts induced variable increase in antioxidant defense enzymes activities (catalase, superoxide dismutase (SOD) and peroxidase) in liver and kidney tissues of B(a)P-treated mice. However, catalase, SOD and peroxidase activities in the liver were significant increased with 1.7 - 2.45, 1.81 - 4.23 and 1.3 - 3.2, respectively times of the control group (B(a)P-mice). Also, their algae extracts were increased the cellular glutathione (GSH) level ranged from 7.3 to 9.4 μmol g-1 when compared with B(a)P group (2.1 μmol g-1). The algae extracts were inhibited the induction of lipid peroxidation product, when determined in liver (61.47 -79.40%) and kidney (65.67- 81.74%) homogenate of B(a)P-mice as thiobarbituric acid reactive substance (TBARS). The dietary administration of β-carotene and Vit. E mixture was induce increased activities of GST, catalase, SOD and peroxidase and increased the cellular GSH level and inhibited the induction of lipid peroxidation product of B(a)P-mice. These findings support the hypothesis that lipophilic algae extracts (rich in antioxidant compounds) alters the protective ability of tissues against carcinogenesis and oxidative stress caused by B(a)P in vivo.