ABSTRACT The insulin receptor is a dynamic cellular macromolecule that moves through various compartments of the cell throughout its lifetime. This review addresses the processes involved in the synthetic assembly of the insulin receptor; the interaction of insulin with the receptor protein; the receptor-mediated endocytosis of insulin; and the role of receptor tyrosine and serine phosphorylation in both endocytosis and recycling. This discussion is concluded by examining the data available on the intracellular inactivation and degradation of the receptor protein. Emphasis is given to the cellular regulation imposed at each of these steps in receptor processing, and how the use of pharmacologic and physiologic perturbants has afforded experimental insights into the mechanisms the cell utilizes in modulating the expression and functioning of the insulin receptor.-Knutson, V. P. Cellular trafficking and processing of the insulin receptor. FASEB J.