abstract the chemotaxonomy of moroccan rosemary was studied. the essential oil, which was obtained by hydrodistillation of rosmarinus officinalis l. from different regions of morocco (rabat, taforalt and elateuf) was analyzed by gc and gc/ms. the variations in chemical composition are important between plant populations. we have defined three chemotypes of r. officinalis: the -pinene-chemotype (-pinene, 37-40% of the oil), the camphor-chemotype (camphor, 41-53% of the oil) and the 1,8-cineole-chemotype (1,8-cineole, 58-63% of the oil). the chemical composition of the 1,8-cineole-chemotype of r. officinalis was analyzed by gc and gc/ms. a total of 91 constituents were identified. the effect of harvest time on the oil production and chemical composition was examined on r. officinalis, and r. eriocalyx jordan et fourr., which were collected in the eastern morocco from elateuf and debdou regions at different vegetative stages (from january to july). at full flowering, the oil yield was particularly high (1.6 % for r. officinalis and 1.9 % for r. eriocalyx). it was much lower for early or late flowering. the chemical composition of oils does not seem to be a function of the species differentiation or harvest time. 1,8-cineole (48,9-56,3%) was the main component of the oils of both species.