A practical guide to the use of polymerase chain reaction (PCR) to help examine, on a molecular and cellular level, how toxic responses are manifested. It offers a basic understanding of PCR and its optimization, as well as describing specific, high-impact areas of molecular toxicology and recent advances. The following techniques are described in detail: quantitative reverse transcriptase PCR and methods to examine gene expression, differential display cloning, cloning and library screening by PCR, genotype and polymorphism analysis of drug and toxicant metabolizing enzymes, basic, non-PCR based molecular biology methods. Shows both novices and experienced PCR practitioners how to use PCR to its fullest potential.