This is a 2-yr, double-blind, placebo-controlled study of administration of an oral GH secretagogue (MK-677) in 72 healthy older adults. Effects of MK-677 on endogenous GH secretion, body composition, aerobic exercise capacity, isokinetic muscle strength, functional performance, flexibility, balance, glucose and insulin sensitivity, bone mass and lipids will be determined. Several questionnaires will assess the subjects sense of general well-being, perception of health and quality of sleep.