Several species belonging to the Hyptis (Lamiaceae) genus represent an important source of bioactive constituents, which are reputed for their wide range of antimicrobial, anticancer and insecticidal activities. The volatile oils obtained from various parts of the Hyptis plants were found to be primarily composed of mono- and sesquiterpenes. Significant differences were observed in the percentage compositions of the major components, which allowed for differentiation among the species. Based on the dominant constituents, phylogenetic relationships were found to be common among some species: 1,8-cineole (H. fruticosa, H. goyazensis, H. martiusii and H. suaveolens); beta-caryophyllene (H. marrubioides, H. pectinata, H. spicigera and H. suaveolens); eugenol (H. recurvata and H. suaveolens); gamma-cadinene (H. glomerata and H. ovalifolia); p-cymene (H. mutabilis and H. pectinata); alpha-pinene (H. crenata and H. emoryi). The monoterpenes, alpha-pinene and p-cymene were detected at various concentrations in all the Hyptis oils investigated. This paper reviews the essential oil compositions of eighteen Hyptis plant species studied in various parts of the world covering the publications of 100 years (1909 to 2009) after the first article appeared in the literature.