The genus Ocimum (Lamiaceae) is distributed all over the world and can be found in many environments. Ocimum species is a rich source of various phytochemicals including tannins, phenolic acids, anthocyanins, phytosterols, and policosanols. These phytochemicals have the potential to significantly impact human health. The economic importance of Ocimum is also evident; Ocimum oil and its constituents and derivatives are used as flavoring agents throughout the world in food, pharmaceutical, herbal, perfumery, and flavoring industry. The important advantages of Ocimum plants in various treatments are their safety besides being less expensive, efficacy and availability throughout the world. This paper will focus on the biological effects of Ocimum essential oils, with particular attention on the molecular mechanism underlying their action.