This collection explores detailed experimental protocols necessary for setting up a variety of in vitro cytochrome P450 (CYP) assays that are vital in selecting drug candidates in a drug discovery pipeline. Major factors affecting drug metabolism include CYP expression levels, kinetic parameters for individual CYP enzymes, CYP inhibition and induction, time-dependent inhibition (TDI), CYP stability, non-CYP stability, UDP-glucuronosyltransferases (UGT) stability, excretion mechanisms, and drug-drug interactions (DDI), all addressed in this volume. Written for the Methods in Pharmacology and Toxicology series, chapters include helpful background information on the in vitro assay, a list of all the materials, reagents, and equipment necessary to carry out the assay, a step-by-step protocol, notes containing common and unexpected experimental problems in the assay, as well as references containing important supplementary reading.