The composition of the steam-distilled oil from the roots of 9-month-old field-grown Valeriana officinalis var. sambucifolia was analysed and compared with that from Agrobacterium-mediated transformed roots of the same species. Capillary GC and GC-MS studies revealed that the normal oil contained bornyl acetate (13.3%) and valerenal (12.4%) and the transformed oil kessane derivatives, tentatively identified as kessyl alcohol (10.5%) and kessyl acetate (10.4%), as the main constituents.