The following study is concerned with two Eucalyptus species acclimatized during the last century in Egypt viz., Eucalyptus camaldulensis var. camaldulensis Dehn and Eucalyptus citriodora Hook. with an attempt to evaluate their potentialities as useful candidates in the national herbal drug industry. The plan of work included: A. A comparative analysis of the DNA profiles of the leaves of Eucalyptus camaldulensis var. camaldulensis Dehn. and Eucalyptus citriodora Hook. B. A comparative proximate analysis and phytochemical screening of the leaves of the two species under investigation. C. A comparative chromatographic analysis of the different extracts of the leaves of the two cited plants D. A comparative investigation of the lipoidal composition of the leaves of both plants. E. A detailed physico-chemical investigation of the hydrodistilled essential oils of the leaves of the two species and the study of the effect of seasonal variation on their individual composition. F. An assessment of the bioactive potentialities of the leaves of the plants carried out on both the total alcohol extracts and essential oils prepared.