Abstract The essential oils of rosemary (Rosmarinus officinalis L.) from three locations in Lebanon were extracted by steam distillation and their chemical composition was determined by GC/MS. The plants were collected during two years at either flowering stage or after. The oils obtained did not show appreciable differences in their composition in relation to geographical region. The three oil samples were found to be rich in Î±-pinene (18.8â38.5%) and 1,8-cineole (19.1â25.1%). The Lebanese oils had particularly high levels of Î±-terpineol (2.9â11.2%) and geraniol (1.8â9.3%). Although the results obtained did not indicate a large variation of oil composition in relation to harvest time (flowering and after flowering), some reproducible differences were noticeable. A parallel study on rosemary leaves and flowers from one of the three locations showed that their oils had the same chemical composition.