Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility in women. Disordered folliculogenesis in PCOS has long been characterized by three phenomena: (1) the accumulation of small follicles, (2) inhibition of follicular maturation, and (3) absence of follicular turnover. These defects presumably prevent ovulation, but have never been explored in vivo. An accurate understanding of antral follicle development in PCOS is critical to facilitate the diagnosis and identify targets for nutritional and pharmacologic interventions aimed at reinstating ovulation. The central objective of this dissertation was to characterize antral folliculogenesis in women with PCOS. In Part 1, we used serial ultrasonography to assess follicle growth and regression during a 4–5-week interval. Anovulatory cycles were considered in Chapter 1. We documented active components of follicle development amidst follicular excess in PCOS, and revealed that follicles become arrested at the mid-antral stage, but turnover more frequently than in normal ovaries. Sporadic ovulatory cycles were considered in Chapter 2. We observed earlier selection in women with PCOS than in regular ovulatory cycles and identified potential relationships between milder reproductive features and likelihood of sporadic ovulation. In Part 2, we began to explore the implications of disordered antral folliculogenesis on the diagnosis of PCOS and treatment of anovulation. The clinical utility of the sonographic criteria for PCOS were considered across the menstrual cycle in Chapter 3. We demonstrated that diagnostic markers of follicular excess are robust over time irrespective of cycle phase. Nutritional therapies for anovulation were reviewed in Chapter 4. We described the limitations of previous studies and identified opportunities for future research in the field. Collectively, this dissertation integrated ultrasonographic approaches from basic science to inform and improve the clinical management of women with PCOS.