This collection presents novel insights into the micro- and macro-variation of causal clauses from a cross-linguistic perspective. It contains a general introduction to the topic setting the scene and nine chapters based on data from Dutch, German, English, Icelandic, Chinese, and Japanese. Topics discussed in the individual chapters involve, inter alia, external, internal and linear syntax of adverbial clauses expressing a causal relation, their semantic interpretation and information-structural properties, verb position, volitionality, and the development of particular causal conjunctions. The findings gained here are of synchronic and diachronic nature and offer new theoretical perspectives on how causal dependency relationships are expressed by inherent causal morpho-syntactic patterns. They also provide a deeper comprehension of how sentential modifiers work, emerge, and develop in general. This volume is an asset to grammarians, syntacticians, theoretical, and historical linguists.