Follicle Stimulating Hormone is involved in male and female fertility as a component of the HPG Axis. Its functions include spermatogenesis in males and ovarian follicle development in females. To better understand the physiology of this hormone and its effects, we focused on the receptor for hFSH (hFSHR) and its location on the cell membrane. Previous work in our lab has demonstrated that hFSHR localizes in lipid rafts. These are dense regions of the cellular membrane with high levels of cholesterol and sphingolipids. What is unclear is how the receptor gets into the lipid rafts. To study the interaction between hFSHR and caveolin of lipid rafts, I examined the properties of the lipid rafts and their sensitivity to various detergents. This was done to verify that regions of the membrane where hFSHR was located were detergent resistant. This study was performed using a discontinuous Optiprep Density Gradient and then verifying the location of the hFSHR using western blot analysis. The results showed that lipid rafts are resistant to some mild detergents such as Triton, but were disrupted by stronger ones such as SDS. I also used the methods of immunoprecipitation and western blot analysis to directly study the interaction between caveolin proteins and hFSHR. Experiments have suggested that the caveolin protein is closely linked with the receptor. Future experiments will build off these results and make use of caveolin mutants produced in the Cohen Lab to determine how changes to caveolin interfere with hFSHR function by measuring levels of downstream signaling molecules. This has potential implications in developing contraceptives and possible treatments for fertility treatments involving the action of FSH and its receptor.