While common marmosets are increasingly used as alternative primate models in biomedical research, their life history, specialized behavior and unique physiology are not well known. This paper describes important marmoset attributes that are particularly relevant for biomedical research, including reproduction, neurobiology, immunology, endocrine signaling, obesity and aging, in addition to fetal and postnatal development. While common marmosets exhibit characteristic anthropoid primate traits, they clearly differ from Old World primates and humans in a variety of functions, including reproduction, endocrine signaling and immunology. These differences, however, permit the use of common marmosets in unconventional research strategies targeted on human pathology.