Adverb positions vary within a single language as well as across diverse languages. Based on the study of adverbs in English, French and German, this monograph shows that the distribution of adverbs is influenced by various factors at distinct levels of linguistic representation - comprising semantics, syntax, phonology and information structure - which interact in determining adverb positions. The results of the investigation are formulated within the theoretical framework of Optimality Theory, which captures the complex interaction of these factors by hierarchically ranked constraints, deriving cross-linguistic variation of adverb positions by differences in the language-specific constraint hierarchies. The book is divided into two parts: While Part I examines adverb positions in general, Part II investigates under which circumstances an adverb may attach to a phonetically empty constituent in the languages under discussion. The book appeals to a linguistic audience interested in Germanic and Romance languages as well as in theoretical syntax in general.