This book discusses the origin and history of the grammatical category of gender in the Indo-European family of languages. Gender systems of Proto-Indo-European (PIE), and of the various daughter languages are assessed from historical, typological, and areal points of view. In addition, common properties and tendencies (or drift) in the development of gender in different Indo-European branches are presented. The formal and semantic principles of gender assignment in PIE are examined on the basis of a reconstructed lexicon of PIE nouns, and the scope of gender agreement in the proto-language is reconstructed by comparing the agreement rules in the early Indo-European dialects. The Early PIE two-gender system and the development of the feminine gender in Late PIE are also discussed, and finally the PIE gender system is contrasted with the typologically rather different gender systems found in the neighboring areas of Eurasia.