In spite of the importance of the corpus luteum in human reproduction, little is known about its formation after ovulation and during regression in the absence of conception. This is largely due to constraints on the availability of normal human tissue; therefore an appropriate model which could be studied and could provide information applicable to the human was sought. The baboon (Papio), a non-human primate, has been determined to be one such model. Thus, in the past several years our studies have examined the role of luteal peptides in corpus luteum function, and, when possible, we have attempted to examine corpora lutea from the human and baboon in parallel. Although a milk-ejection factor was recognized to be present in luteal tissue in 1910 (Ott and Scott, Proc. Soc. Exp. Biol. Med., Vol. 8, p. 49), the role of oxytocin in luteal physiology has not been easy to ascertain. This is in part due to the methodologies employed to assess its role. Our studies summarized below suggest that oxytocin does not directly affect luteal steroidogenesis but that it may play a role in cell to cell communication involving the expression of the gap junction proteins, the connexins. In view of the fact that oxytocin, its receptor, gap junctions and associated proteins are not unique to the human and non-human primates, the model of luteal development and demise proposed may be applicable to most species.