The concept of frailty as a health dimension in old age is recent and has its origin in the development of geriatric medicine. Initially an unformulated clinical intuition, it is now defined by a diminished physiological reserve of multiple organs that exposes older individuals to increased vulnerability to stressors and a higher risk of adverse outcomes. The operational definition of frailty, however, is still debated. From a diversity of models, two emerged in the early 2000s from epidemiological studies conducted in large population-based aging cohorts. The body of research emphasized prospective associations between a frailty phenotype and a range of adverse outcomes or between a frailty index measuring the accumulation of deficits and death. A few studies showed promising spontaneous remissions in the early stages of frailty, raising expectations for effective interventions. Transitions between frailty stages and effective interventions on frailty nevertheless remain two fields needing further investigation. More recently, these tools have been applied as screening instruments in clinical settings to guide individual decision-making and orient treatments. New questions are raised by the use of instruments developed to screen frailty in epidemiological research for assessing individual situations. Inquiring whether frailty screening is relevant opens a Pandora’s box of doubts and debates. There are many reasons to screen for frailty both from a public health and a clinical perspective that are only exacerbated by the current demographic evolution. Open questions remain about the feasibility of frailty screening, the properties of screening tools, the relevance of an integration of socioeconomic dimensions into screening tools, and the effectiveness of interventions targeting frailty. Fifteen years after the publication of the Fried and Rockwood landmark papers proposing operational definitions of frailty, this article presents an overview of current perspectives and issues around frailty screening in populations and in individuals.