Drug development often fails because of poor pharmacokinetic (PK) properties of the drug candidate. For minimizing the risk of such failure, selection of compounds having good PK properties is required in the early stage of a drug discovery program in which, however, large numbers of compounds still prevail. Therefore high-throughput PK measuring methods are urgently needed. In a somewhat later stage, but still in the preclinical setting, metabolic and PK data from man or from transgenic ('humanized') animals are highly desirable. This is particularly true for chronic diseases, in which long-term drug effects and the modification of disease processes are critical. For research on drug metabolism and drug toxicity during drug development, animal models are commonly used. However the choice of the animal species as a predictive model for the human condition is often inadequate due to large and unpredictable species differences. Therefore, it is important to develop in vitro metabolism and toxicity tests with human and animal tissues not only in liver but also in intestinal, kidney and lung tissue.