(+)-cis-Sabinene hydrate and (+)-trans-sabinene hydrate are the main monoterpenes found in marjoram (Origanum majorana), but can also be found in other Origanum species as well, as in e.g. Melaleuca alternifolia. The synthesis of sabinene hydrate in marjoram (Origanum majorana) is performed by sabinene hydrate synthase. It is claimed, that both, (+)-cis- and (+)-trans-sabinene hydrate are produced by the same enzyme in an exact ratio of 10:1. To verify this in vitro result in vivo, we analysed single plants of 20 different genotypes of Origanum majorana and of three different populations of Origanum microphyllum and calculated the ratios of (+)-cis- to (+)-trans-sabinene hydrates. In Origanum majorana a constant ratio of 20:1 could be found, whereas in Origanum microphyllum the ratio did not prove to be constant.