In this paper, we present an overview of classical genetic markers in nonhuman primates and then contrast the discriminatory powers of these markers with DNA markers. We have restricted the scope of our discussion to genetic markers found in blood, since they have been studied most extensively over the past 30 years. For example, immunoglobulin allotypes, complement markers, transferrins, and other protein markers can be identified using serum or plasma. Lymphocytes carry the major histocompatibility complex (MHC) markers, which are very polymorphic in most nonhuman primates. Lymphocytes are also used as a source of DNA. Finally, red blood cells carry an enormous array of blood group as well as isozyme markers. Our discussion will be limited to three species: rhesus monkeys (Macaca mulatta), baboons (Papio hamadryas), and chimpanzees (Pan troglodytes), although the principles are applicable to all nonhuman primates.