This monograph provides an in-depth investigation of the structural integration and the licensing of adverbs in relation to clause structure, with special emphasis on the structural implementation of the relation between the position and interpretation of adverbs. The book substantiates the hypothesis that the licensing of adverbs within and across the three layers of the clause is contingent on specifier-head agreement and that variation in the linear order of adverbs and other elements of the clause follows from the interplay of a small number of factors. The central claims made are: functional projections hosting adverbs are not confined to the inflectional and complementizer layer of the clause, but also play a central role in the shaping of the lexical layer; postverbal adverbs are realized within a semantically empty verbal projection and licensed under specifier head agreement by proxy; and adverbs that occur within the complementizer layer of the clause do so by either move or merge.