A germplasm collection ofArtemisia annuaL. consisting of 13 accessions was field grown. The essential oil, which was obtained from dry leaves and flowers by hydrodistillation was analyzed by GC and GC/MS for essential oil composition. The oil content of leaves ranged from 0.84% to 1.51% (volume/dry weight) with individual plants as high as 2.35%. Thirty-two constituents were identified in the oil of the leaves and flowers, and the greatest concentration of oil was found in fully mature leaves (47% total oil/plant), the middle third portion of the foliage. The major components of the oil include: artemisia ketone (35.6%) and 1,8-cineole (28.1%) in the leaves of early summer harvested plants, artemisia ketone (26.8%) and camphor (20.5%) in leaves of fall harvested plants, and artemisia ketone (56%) and camphor (10.5%) in flowers of fall harvested plants. Certain accessions which were rich in specific constituents (as % of essential oil) were identified, e.g., artemisia ketone (68.5%), camphor (27.5%), 1,8-cineole (22.8%), α-pinene (16.0%) and camphene hydrate (12%). Plants within accessions also varied in essential oil composition.