Frailty has become a topic of increasing interest in health care. No longer treated as a catch-all term for agedness, decline and disablement it has acquired a more precise definition, applied to those individuals whose ‘aged’ state is seen to put them at risk of adverse outcomes. This transformation is we argue the outcome of a more general differentiation of terms that were previously used to categorize the weak and marginal within society. Old age re-labelled as ‘later life’ has become re-articulated as a successful life stage relatively free from impairment. Disability has been re-positioned and its links with impairment attenuated while chronic illness has acquired a new narrative of its own. This has left frailty behind, redolent still with all the old negative attributes of marginality, but now more than ever evacuated of any remaining elements of ‘status’ or ‘agency’. Frailty is defined less by the identities of those who are deemed frail than by what frailty seems to augur in its direction of travel — a journey towards unspecified adverse outcomes. This re-positioning, we suggest, helps lay the foundation of a social imaginary of ‘the fourth age’ as the new location of old age.