Modulatory effects observed due to clove administration (0.5%, 1% and 2% w/w in the diet) to Swiss albino mice for 10, 20 and 30 days in the hepatic levels of cytochrome P-450 (Cyt. P-450), cytochrome b5 (Cyt. b5), aryl hydrocarbon hydroxylase (AHH), glutathione S-transferase (GST), DT-diaphorase (DTD), acid soluble sulfhydryl (SH) content and radiation-induced malondialdehyde (MDA) formation were recorded. Enhanced GST, Cyt. b5 and SH levels were observed in all the treatment groups, excepting those maintained on a 0.5% diet for 10 days which did not show significant increase in the GST and SH levels as compared to their respective controls. Significant reduction in Cyt. P-450 and MDA levels was observed in all groups at 30 days duration. While AHH levels remained unaltered by clove administration, DTD activity was elevated by 1% and 2% clove diets at 30 days duration. An in vivo bone marrow micronucleus assay demonstrated that administration of 0.5% and 2% clove diets for 10 days neither significantly induced micronuclei nor could effectively modulate the 7, 12-dimethylbenz[a]anthracene genotoxicity in mice. The results suggest whole cloves as potential chemopreventive agents.