The activity of a methanol extract of radish sprouts for the induction of nicotinamide adenine dinucleotide (phosphate) NAD(P)H/quinone reductase (QR), which plays critical roles in protection against chemical carcinogens and other toxic xenobiotics, was examined in murine Hepa1c1c7 cells. The methanol extract induced QR activity in a dose-dependent manner in the concentration range of 0.2 to 1.6 mg/mL with a maximum of a 3.5-fold increase in induction. The induction of QR by the extract was regulated at the transcriptional level. Using a Western blotting analysis and Ah-receptor-defective mutant of Hepa1c1c7 cells (BPrc1 cells), the extracts at a concentration of 0.8 mg/mL or lower was found to be a monofunctional inducer and caused no elevation in cytochrome P-450 level that may activate carcinogens. The dichloromethane (CH2Cl2) fraction of the extract showed the highest induction potency while the other fractions were less potent. These results indicate that radish sprouts can be regarded as a safe and promising new dietary source for decreasing the risk of developing cancer.