In this article, I examine how repairs in adult-child conversations guide children's acquisition of language. Children make unprompted self-repairs to their utterances. They also respond to prompts for repair, whether open ("Hm?," "What?") or restricted ("You hid what?"), and to restricted offers (Child: "I falled," Adult: "You fell?"). Children respond to clarification requests with self-repairs in the next turn, and make use of the feedback offered. The contrast between their utterance and the adult utterance identifies the locus of the error (negative feedback), while the adult's offer presents a conventional version of the child's utterance (positive feedback). I describe the use of restricted offers in conversations with children acquiring English and French, then present two case studies of how these inform children about homophonous French verb forms and early opaque Hebrew verb uses. These findings demonstrate the fundamental role of repair in the acquisition of a first language. [This article was presented at the meeting of the Society for Text and Discourse, The New School, New York City, in July 2019.]