abstract the two essential oils isolated from plants of hyssop (hyssopus officinalis l. ssp. officinalis) grown in two different localities near urbino (marche, italy) were analyzed by gc and gc/ms. the major components were pinocamphone (34% and 18.5%), isopinocamphone (3.2% and 29%) and -pinene (10.5% and 10.8%). the major differences in the composition of the oils were detectable in the ratio of pinocamphone/isopinocamphone, in the percentage of linalool (0.2% and 7.9%) and camphor (0.3% and 5.3%). the oils showed antifungal activity against 13 strains of phytopathogenic fungi; the activity of the oil extracted from plants grown at 1000 m above sea level showed higher activity.