Essential oils of young and mature rhizomes, air-dried and steamed rhizomes, and seed rhizomes of Zingiber officinale Roscoe (ginger) were prepared, and their inhibition of filamentation by Candida albicans was examined. Ginger essential oils, and particularly those from seed and air-dried rhizomes, had potent inhibitory activity compared to ginger oleoresins obtained by ethanol and hypercritical carbon dioxide extraction and essential oils of 5 other plants in the family Zingiberaceae. Of the constituents, [6]-shogaol was most active against filament formation and growth of C. albicans, followed by citral and [6]-gingerol. Ginger oleoresin, and especially that obtained by ethanol extraction, with a high [6]-gingerol content exhibited potent scavenging activity against 1,1-diphenyl-2-picrylhydrazyl radicals in comparison to essential oils of ginger and other Zingiberaceae plants.