Polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility, is characterized by increased ovarian androgen production, arrested follicle development, and is frequently associated with insulin resistance. These PCOS phenotypes are associated with exaggerated ovarian responsiveness to FSH and increased pregnancy loss. To examine whether the perturbations in follicle growth and the intrafollicular environment affects development of the mature PCOS oocyte, genes that are differentially expressed in PCOS compared to normal oocytes were defined using microarray analysis. This analysis detected approximately 8000 transcripts. Hierarchical clustering and principal component analysis revealed differences in global gene expression profiles between normal and PCOS oocytes. 374 genes had a statistically-significant increase or decrease in mRNA abundance in PCOS oocytes. A subset of these genes was associated with chromosome alignment and segregation during mitosis and/or meiosis, suggesting that increased mRNAs for these proteins may negatively affect oocyte maturation and/or early embryonic development. Of the 374 differentially expressed genes, 68 contained putative androgen receptor, retinoic acid receptor, and/or peroxisome proliferating receptor gamma binding sites, including 9 of the genes involved in chromosome alignment and segregation. These analyses demonstrated that normal and PCOS oocytes that are morphologically indistinguishable and of high quality exhibit different gene expression profiles. Furthermore, altered mRNA levels in the PCOS oocyte may contribute to defects in meiosis and/or mitosis which might impair oocyte competence for early development and therefore contribute to poor pregnancy outcome in PCOS.