Frailty is a pre-disability syndrome where an older person can be identified as being at risk when exposed to stressors associated with high risk for disability or needing to be hospitalized. Two major frailty definitions exist. The physical phenotype of frailty and the multiple deficit model. A simple frailty screening tool—FRAIL—has been validated. Treatment of frailty involves resistance exercise, optimization of nutrition, and treatment of fatigue (sleep apnea, depression), treatable causes of weight loss and adjustment of polypharmacy. Sarcopenia (decline in function with low muscle mass) is a major cause of frailty. A simple sarcopenia screening tool—SARC-F—has been validated. The multiple causes of sarcopenia are reviewed. Optimal treatment is resistance exercise, leucine-enriched essential amino acids and vitamin D replacement.