The theoretical issues addressed in the present volume are semantic and cognitive properties of reciprocal events, syntactic properties of reciprocals, and the relationship of reciprocals to other grammatical categories. Several papers discuss the history of reciprocal constructions, offering alternative hypotheses regarding the grammaticalization of reciprocals. The formal, functional, typological and historical approaches in the present volume complement each other, contributing together to the understanding of forms, and syntactic and semantic properties of reciprocal markers. Several paper.