The essential oils ofAgathosma betulina, A. crenulataand their hybrids were analyzed to determine whether the taxa could be distinguished by their monoterpene chemistry. Pulegone was found to be the key component for identification of the oils.A. betulinais identified by a pulegone content of 2.4% to 4.5%, the hybrids have 7.6% to 27.8% andA. crenulatahas 31.6% to 73.2% pulegone.A. betulinaand the hybrids have a higher content of 8-mercapto-p-menthan-3-one than 8-acetylthio-p-menthan-3-one while, the reverse is true forA. crenulata.The cis-8-mercapto-p-menthan-3-one content is higher than that of the trans- isomer forA. betulinaand die hybrids, but the reverse is true forA. crenulata.TwoA. betulinachemotypes were identified. The Diosphenol chemotype is characterized by high ϕ-diosphenol (>10%) and diosphenol (>12%), and low isomenthone (<29%) concentrations. The Isomenthone chemotype is characterized by high isomendione (>31%) and low ϕ-diosphenol (<0.16%) and diosphenol (<0.14%) concentrations. No chemotypes were found forA. crenulata, and those found for the hybrids were not significant due to the small sample size. No significant correlation was found between oil composition and geographic origin for any taxon. The Isomenthone chemotypes ofA. betulinaare restricted to the Piketberg mountain range.