This review summarizes recent studies pertaining to follicular development in the human ovary. Some of these studies were concerned with characterizing the steroidogenic capacity of the individual cell types of the follicle in relation to whether the follicle was healthy or atretic. Other studies covered in this review concern the oocyte and its hormonal environment both in vivo and in vitro, the effects of steroids and gonadotrophins on the steroidogenic potentials of follicle cells and also some endocrine and non-endocrine responses of thecal and granulosa cells after being separated and then recombined in vitro. The data are integrated in relation to the development of a follicle during the follicular phase of the menstrual cycle.