Repair refers then to an organized set of practices through which participants in conversation are able to address and potentially resolve problems of speaking, hearing or understanding. Repair then is a procedural, party-administered, locally-managed, recipient-designed, means by which understanding in talk is accomplished, maintained, and defended within the sequential contexts of talk-in-interaction. In describing the organization of repair it is usual to use the term “self” for the speaker of the trouble source and “other” for any other participant. The essay discusses and contrasts self-initiated, self-repair (SISR) and different forms of other-initiated, self-repair (OISR). It points out how repair functions as a vehicle for action. Most of the research discussed is based on the analysis of English materials, but a number of recent studies have taken a comparative perspective looking at the organization of repair across differences of language, culture and social arrangement. The essay also addresses repair in child language development.