Abstract The essential oil, obtained by steam distillation of Argania spinosa's leaves, an endemic tree of Morocco, was investigated by GC and GC/MS. The compounds were characterized by their mass spectra and retention indices. The oil was mainly composed of sesquiterpene alcohols and hydrocarbons. The principal constituent was 1,10-di-epi-cubenol (20.5%). The oil was shown to inhibit the growth of three strains of Gram positive and four strains of Gram negative bacteria as well as three strains of yeast and four strains of mold