This article provides a research programme in which typological patterns are ultimately explained in terms of language processing and use. It presents three general organizing principles that describe common patterns in grammars and performance: Minimize Domains, Minimize Forms, and Maximize Online Processing. The first is illustrated with patterns involving relative clauses; the second, with morphological data and markedness hierarchies; and the third, with a number of linear precedence regularities that hold across different language types. The article finally outlines some general issues raised by this approach to linguistic typology, and discusses challenges that remain. It is concluded that typological patterns can be profitably described, predicted, and to a significant extent explained in terms of principles of efficiency and complexity in processing. These principles, individually and in combination, can motivate a broad range of preference data in performance and in grammars.