The chemical composition of the leaf/inflorescence oil ofSeriphidium brevifolium(Wall.) Y. Ling et Y. R. Ling which was obtained from mature and immature plants collected in an inner valley of Kumaon Himalaya, was examined by GC/M S. Forty-six constituents were characterized in the “immature oil” and 63 constituents were identified in the “mature oil.” The main components of “immature oil” were α-thujone (77.0%), β-thujone (4.4%) and 1, 8-cineole (3.3%), while the “mature oil” possessed α-thujone (60.2%), β-thujone (5.5%) and 1, 8-cineole (1.5%). The reason for a preference for the use of the immature leaves/inflorescence as an incense over the mature leaves/inflorescence is thought to be due to the higher total thujone and 1,8-cineole content of the oil.