Ergativity is one of the main challenges both for linguistic and acquisition theories. This book is unique, taking a cross-linguistic approach to the acquisition of ergativity in a large variety of typologically distinct languages. The chapters cover languages from different families and from different geographic areas with different expressions of ergativity. Each chapter includes a description of ergativity in the language(s), the nature of the input, the social context of acquisition and developmental patterns. Comparisons of the acquisition process across closely related languages are made, change in progress of the ergative systems is discussed and, for one language, acquisition by bilingual and monolingual children is compared. The volume will be of particular interest to language acquisition researchers, linguists, psycholinguists and cognitive scientists.