In the present study, the induction of drug-metabolizing enzymes and transporters was evaluated by analyzing mRNA expression in human hepatocytes after exposure to various compounds. The compounds tested included typical enzyme inducers, rifampicin and omeprazole, and controls. All experiments were performed in the presence of 0.1% DMSO. Analysis was performed by the real-time reverse-transcription polymerase chain reaction method (RT-PCR) in the presence of TaqMan probes using an ABI PRISM 7700 Sequence Detector system. A new analytic method to quantify mRNA levels in small numbers of human hepatocytes has been developed for phase I enzymes, phase II enzymes, and transporters. The levels of CYP1A1, CYP2B6, CYP2C8, CYP3A4, CYP3A5, ADH3, and ABCG1 mRNA in human hepatocytes increased after exposure to rifampicin. The levels of CYP1A1, CYP2B6, CYP3A4, CYP3A5, and ABCG1 mRNA recovered after a change to media without rifampicin. The levels of CYP1A1, CYP1A2, CYP1B1, ALDH3, and ALDH6 mRNA increased after exposure to omeprazole, and recovered after a change to media without omeprazole. On the other hand, the levels of ADH3 and ABCB4 mRNA decreased after exposure to omeprazole, and recovered after a change to media without omeprazole. In conclusion, these results demonstrate the applicability of quantitative real-time RT-PCR to the evaluation of the gene induction and recovery of drug-metabolizing enzymes and transporters after exposure to drugs in human hepatocytes.