In this book, the secondary metabolites of both flowers and leaves of O. sanctum, O. basilicum and O. americanum, three species which occur in the central Sudan, were compared. The chemical proximate of aerial parts of three Ocimum spp. (O.sanctum, O.basilicum and O.americanum) was also analyzed using standard analytical methods. Preliminary phytochemical screening for carbohydrates, reducing sugars, monosaccharides, Tannins, saponins, flavonoids, terpenoids, steroids, alkaloids, proteins, amino acids and anthraquinones were performed for each plant species under study. Chromatography examination by using thin layer chromatography (TLC) exhibit good separation of spots indicating the probability of alkaloids, flavonoids, saponins and tannins in plant species under study.Using gas chromatography ¿ mass spectrometry (GC/MS) analysis of n-hexane extracts, most of the identified compounds in the extracts were terpenoids.The results obtained show that Ocimum spp. is a good source of food and therapeutic agent which will be of use for food and pharmaceutical industries. Information about the chemical composition of the oil could then be useful in the classification of these plants.