The chemical composition of the peel essential oil (PEO) of Citrus deliciosa Ten. growing in Egypt was investigated using gas chromatography-mass spectrometry(GC-MS) analysis .As a result, sixteen components were identified representing 98.79% of the total oil yield(0.55 %v/w).The major components belong to monoterpene -type viz., d-limonene (46% ),p-cymene(40%) and ɣ -terpinene (9%). Consequently , PEO of C. deliciosa Ten . belonged to d-limonene/p-cymene chemotype. The PEO was screened for the antimicrobial activity and it showed observed inhibitory activity against Gram-positive bacteria (Bacillus subtilis ,Staphylococcus aureus) and marked inhibition against fungi ( Aspergillus flavus ,A . niger and Candida albicans ) but no activity was detected against Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa). The induction of the phase II detoxifying enzymes like glutathione- S- transferase (GST) and glutathione peroxidase (GPx) was investigated in a way to evaluate the chemoprevention and/or chemotherapeutic potential of the PEO -alone and in combination with vitamin E on rat alimentary tract. An increase of 2.72 and 2.12-folds in GST activity in liver and intestinal mucosa in addition to 50.4% increase in large intestinal mucosa was observed with PEO gavaging .On the other hand ,PEO alone had no significant effect on GPx enzyme activity in all the tested tissues except liver. A combination of vitamin E with each of GST and GPx led to potentiation of activity of both enzymes. In such a way ,the peels of C. deliciosa Ten. which is normally considered as environmental waste is turned into promising antimicrobial, chemopreventive and/or chemotherapeutic nutraceutical or pharmaceutical product with an extra added economic value .