The influence of usage frequency, and particularly of linguistic similarity on human linguistic behavior and linguistic change in situations of language contact are well documented in contact linguistics literature. However, a theoretical framework capable of unifying the various explanations, which are usually couched in either structuralist, sociolinguistic, or psycholinguistic parlance, is still lacking. In this introductory article we argue that a usage-based approach to language organization and linguistic behavior suits this purpose well and that the study of language contact phenomena will benefit from the adoption of this theoretical perspective. The article sketches an outline of usage-based linguistics, proposes ways to analyze language contact phenomena in this framework, and summarizes the major findings of the individual contributions to the special issue, which not only demonstrate that contact phenomena are usefully studied from the usage-based perspective, but document that taking a usage-based approach reveals new aspects of old phenomena.