New World monkeys have been used extensively as biomedical models for human diseases, yet little is known about aging in these animals. Life spans in cebids vary, with most species living to approximately 20-30 years of age. Capuchins may be an exception, possibly living as long as 40-50 years. Biomarkers of aging in squirrel monkeys have been studied primarily in relation to the reduced calorie model of aging. These data suggest that squirrel monkeys do not show the same physiological effects of aging as rhesus monkeys and they do not react to a reduced calorie diet the same as rhesus. Cebids are useful in several models of aging, including Alzheimer's disease and cardiomyopathy research. Reproduction in aging cebids has not been extensively studied, but it is known that aging squirrel monkey females experience a reduction in their reproductive potential after the age of twelve. Production of progesterone, estrogen, and bio-LH are all decreased in older squirrel monkey females. They are also prone to a condition similar to pelvic organ prolapse in aging human females. Taken all together very little is known about the reproductive function in aging New World monkeys.