Family socioeconomic status (SES) is related to language development in multiple domains, throughout childhood, and in adulthood as well. Children from lower SES homes show lower levels of language and communicative skill than children from higher SES homes beginning in infancy. The gap between lower and higher SES children persists and sometimes widens with age. Substantial evidence locates the source of these differences in children’s language experience. Children from lower SES homes are talked to less, and the speech they hear is less supportive of language development. The evidence that SES-related differences in parents’ speech cause SES-related differences in children’s language development is consistent with theoretical approaches that give experience an important role in the language acquisition process.