The transcription factor, peroxisome proliferator activated-receptor γ (PPARγ), regulates many processes critical for normal ovarian function. The role of PPARγ in the ovary was investigated by determining its expression throughout the bovine estrous cycle, and luteal tissue was cultured with agonists and an antagonist of PPARγ to determine its impact on progesterone production. Protein, but not mRNA for PPARγ, was lower in regressing compared to functional luteal tissue. Treatment with a PPARγ agonist decreased progesterone secretion from late phase luteal tissue. These findings indicate that PPARγ may play a role in luteal formation/function, and alter progesterone production during specific stages of the ovarian cycle. To facilitate further study of how PPARγ impacts ovarian biology, transgenic mice were developed with the gene for PPARγ specifically disrupted in granulosa cells. Knowing what genes are regulated by PPARγ in the ovary will aid in understanding the mechanisms behind the cyclic pattern of gene expression driving normal ovarian function.