Drug Metabolism and Disposition will consider for publication manuscripts describing the results of original research that contribute significant and novel information on xenobiotic metabolism, transport, and disposition. The term xenobiotic includes therapeutic agents as well as environmental chemicals. Research may involve the use of in vivo or in vitro approaches, including cultured cells and heterologous expression systems. Manuscripts that describe mechanistic aspects of xenobiotic metabolism and transport as well as those examining mechanisms that affect expression and regulation of drug-metabolizing enzymes and transporters, including genetic variability, are encouraged. Manuscripts concerned with genetic, nutritional, or hormonal factors that influence the biological fate of chemicals are also of interest, as are those that address the toxicologic consequences of xenobiotic metabolism. We continue to welcome manuscripts describing metabolite identification and/or identification of specific enzymes responsible for particular metabolic pathways, provided that the studies are thorough and rigorous. Manuscripts presenting the results of pharmacokinetic/pharmacodynamic studies that address mechanisms underlying drug disposition and response and/or address clearly defined hypotheses are invited. Studies lacking mechanistic insight or dealing only with descriptive parent drug pharmacokinetics are not encouraged.