The cloning of the cDNA for human interferon-gamma (IFN-gamma) has resulted in its expression in Escherichia coli, baculovirus-infected insect cells, Chinese hamster ovary (CHO) cells, and the mammary gland of transgenic mice. Large quantities of highly purified recombinant IFN-gamma have been generated, aided by the use of highly specific neutralizing monoclonal antibodies, with a view to its production as a human therapeutic protein. The primary source of structural heterogeneity for IFN-gamma during its production in mammalian expression systems is glycosylation, which can profoundly affect the three-dimensional structure of a glycoprotein and its biological function. A number of analytical approaches have been developed recently to allow a detailed analysis of the carbohydrate structures associated with IFN-gamma, the principal advances being in the areas of capillary electrophoresis and mass spectrometry. The implementation of these high-resolution analytical tools to determine the glycosylation profile of IFN-gamma makes it one of the best characterized recombinant glycoproteins. Recombinant human IFN-gamma acts as a model secretory glycoprotein, typifying the intrinsic glycosylation processing events associated with production of a potential therapeutic glycoprotein.