Major advances in our understanding of the complexities of the perimenopausal process have occurred during the past 5 to 10 years. We now understand that the follicle pool is exhausted at an increasing rate during the last decade of menstrual cyclicity. We are beginning to appreciate that multiple factors, including neuroendocrine changes, may play a role in the perimenopausal period. In addition, it appears that rodents may serve as models for several aspects of menopause.