This book offers a fresh take on several long-standing issues relating to the (non-)truth-conditional interpretation of epistemic, evidential, hearsay and attitudinal sentence adverbials. Drawing on a wealth of data from English and German, it shows for the first time that all four adverbial classes can have both truth-conditional and non-truth-conditional (parenthetical) readings. A novel account is presented according to which (non-)truth-conditional readings may arise at either the syntactic or the pragmatic level. Couched in relevance theory, the book also re-examines the explicature and illocutionary status of the adverbial qualification and the qualified proposition, and refines the notions of pointhood and at-issueness to provide an original information-structural analysis applicable to not just sentence adverbials but a range of other propositional qualifiers. Finally, the investigation identifies five factors affecting (non-)truth-conditional interpretation: linear position, prosody, the semantics of the adverbial, its information-structural properties and the wider context. The book will be of interest to those interested in relevance theory, the semantics/pragmatics interface, the syntax/pragmatics interface and information structure, as well as for syntacticians, semanticists and pragmatists interested in sentence adverbials, other propositional qualifiers and parentheticality, syntactic and interpretational.