Creatine plays a role in cellular energy metabolism and potentially has a role in protein metabolism. Creatine monohydrate supplementation has been shown to result in an increase in skeletal muscle total and phosphocreatine concentration, increase fat-free mass, and enhance high-intensity exercise performance in young healthy men and women. Recent evidence has also demonstrated a neuroprotective effect of creatine monohydrate supplementation in animal models of Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and after ischemia. A low total and phosphocreatine concentration has been reported in human skeletal muscle from aged individuals and those with neuromuscular disorders. A few studies of creatine monohydrate supplementation in the elderly have not shown convincing evidence of a beneficial effect with respect to muscle mass and/or function. Future studies will be required to address the potential for creatine monohydrate supplementation to attenuate age-related muscle atrophy and strength loss, as well as to protect against age-dependent neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease.