The influence of essential oils from naturally occurring plant dietary items such as cardamom, celery seed, cumin seed, coriander, ginger, nutmeg, and zanthoxylum on the activities of hepatic carcinogen-metabolizing enzymes (cytochrome P450, aryl hydrocarbon hydroxylase, and glutathione S-transferase) and acid-soluble sulfhydryl level was investigated in Swiss albino mice. Each oil was fed by gavage at 10 microliters/day for 14 days, and then the animals were sacrificed and their hepatic enzyme activities and sulfhydryl levels were evaluated. Only nutmeg and zanthoxylum oils induced cytochrome P450 level significantly (p < 0.05), whereas cardamom oil caused a significant reduction in its activity (p < 0.05). Furthermore, aryl hydrocarbon hydroxylase activity was significantly elevated only by treatment with ginger oil (p < 0.01), whereas nutmeg oil caused a significant reduction in its activity (p < 0.01). The remaining oils did not significantly alter the level of cytochrome P450 and aryl hydrocarbon hydroxylase activity. Glutathione S-transferase activity was significantly elevated in all experimental groups (p < 0.1-p < 0.001) compared with controls. The acid-soluble sulfhydryl was significantly elevated only by the essential oils of cardamom (p < 0.05), nutmeg (p < 0.05), and zanthoxylum (p < 0.01). Our observations suggest that intake of essential oils affects the host enzymes associated with activation and detoxication of xenobiotic compounds, including chemical carcinogens and mutagens.