Frailty is a common, but under-described, condition in older people, that is now better understood thus aiding better identification and treatment. It is characterised by multisystem deterioration and loss of physiological reserve to cope with insults. The traditional physical phenotype of frailty comprises 5 key findings: weakness, sarcopaenia, weight loss, physical inactivity, and slowness (which are also modulated by psychosocial factors). Several inflammatory, endocrine and nutritional markers have been proposed as contributory, although cause-and-effect is not clear. Predisposing factors are early childhood development and lifestyle, followed by physical inactivity, chronic disease, and anorexia/ malnutrition in later adulthood. These may form a cycle of deterioration. Frailty predisposes to marked decline in physical and mental function resulting from even apparently small insults. This commonly manifests as a "domino" effect, with a small initial insult leading to a cascade of adverse events. Several interventions have been shown to be helpful for frail older adults including exercise programs, nutritional support, maximising function prior to a planned interventions such as surgery, and early intervention when an acute insult threatens independence. Specialist geriatric assessment and management identifies and treats unstable medical conditions, reviews polypharmacy, facilitates early mobilisation, offers nutritional support, and assesses social circumstances. Frail older people in whom function has been compromised may be labelled as "unable to cope" but in fact many benefit from early comprehensive geriatric assessment to enable them to regain lost function.