Women are endowed with only a finite number of oocytes. These oocytes derive from a small population of primordial germ cells (PGC) which migrate to the genital ridge. Little is known about the determinants of germ cell development, migration, maturation and loss. Improving our understanding of these issues is critical to many aspects of reproductive health for women. Our group is studying folliculogenesis: normal, pathological (PCOS) and pharmacological (stimulation for fertility management). Further, our studies span from collaborations with the bench researcher looking at genetic determinants of oocyte endowment and atresia and development of PGC from embryonic stem cells, to clinical studies involving perturbations of the natural system to understand and control folliculogenesis, to epidemiological where we are developing a cohort of 1250 ethnically diverse women to study genetic and clinical markers of ovarian aging. In the short term, these studies may improve ovarian stimulation and diagnostics for ovarian function, as well as improve in vitro culture conditions and the development of oocyte in vitro maturation strategies which would increase the pool of oocytes available for SCNT. In the long term, the knowledge gained will be utilized to treat infertility in women with premature ovarian aging and those at risk for ovarian failure secondary to treatment for malignancy.