Abstract Rosemary oil was isolated from plants collected from five zones in the south of Portugal. The oil yields in fresh material ranged between 0.3â0.7% (v/w). The oils were analyzed by GC and GC/MS and were found to be rich in myrcene (16.6â29.5%), 1,8-cineole (8.3â14.5%) and camphor (14.3â23.1%). Statistical analysis of the results showed that on comparison of the 10 major constituents significant differences were found in the oils obtained from the five different zones.