Publisher Summary This chapter discusses the excretion of pesticides in vertebrates, particularly mammals. Renal and liver function, as they relate to excretion, are summarized as well as the less important routes for excretion of pesticides: respiratory and alimentary. The body, in most cases, because of their lipophilicity takes up pesticides. Before elimination is possible, they must first be metabolized into a form simulating that used by the body for the elimination of endogenous compounds. In general, they are metabolized by phase I and phase II xenobiotic-metabolizing enzymes (XMEs) to conjugation products that are more polar and hence more hydrophilic than the parent compound and then excreted by either the renal or the hepatic route. Although similar anion and cation transport systems are found in both kidney and liver, they differ in the type of excretory products eliminated. In addition to excretion via the bile, highly lipophilic chemicals that are recalcitrant to metabolism may be excreted as the parent chemical by a number of alternate routes, although in terms of the overall excretion of toxicant these are generally of minor importance compared to urine and bile. More obscure routes of excretion including gender-linked routes such as milk, eggs, placenta, and fetus as well as hair, sweat, etc., are briefly mentioned. The role of transporters in cellular elimination is considered, and, finally, the use of excreted pesticides and their metabolites as biomarkers of exposure is summarized.