Abstract The essential oils from fresh plant material of Salvia officinalis L. (sage) were subjected to GC/MS analysis in order to determine the impact of the locality altitudes and seasonal variations on their volatile constituents. The sage plant material was collected from two different localities (altitudes 110 and 400 m) in central Herzegovina near Mostar and at four different stages of development: vegetative period (leaves and stalks, January 2003), prior to flowering (leaves and stalks, April 2003), in the course of flowering (flowering tops, leaves and stalks, May 2003) and after flowering (leaves and stalks, August 2003). The oil yields varied from 0.29% to 1.07%. The qualitative composition of the components appeared to be constant. However, there were notable differences in the amounts of several compounds depending on the stages of plant development. The main components were Î±-thujone (9.3â35.6%), camphor (6.9â29.1%) and viridiflorol (6.0â24.0%). Other important components were Î±-humulene (3.1â13.6%), manool (3.0â13.3%), 1,8-cineole (8.6â12.7%) and borneol (2.0â5.5%).