The present paper offers a synchronic and diachronic analysis of integrated participle clauses or IPCs in English, as found in constructions such as the mayor is busy washing his car or many students had trouble finding the correct answer. Typically, IPCs have developed from adverbial participle clauses into complement clauses. Given their adverbial origins, they can occur as complements to predicates that do not normally take nominal direct objects. Synchronically, criteria are discussed for distinguishing IPCs from adverbial clauses, and it is shown that the distinction between IPCs and adverbial participle clauses is non-discrete. Diachronically, the origins of IPCs are traced, showing that IPCs emerged gradually in the course of the Modern English period. It is argued that initially the primary mechanism of change was (analogically-induced) reanalysis, yet at a later stage IPCs began to assert themselves as a category in its own right, spreading to new contexts through analogical extension. Thus, the discussion illustrates how adverbial clauses can turn into complements, and at the same time shows how a new syntactic (if fuzzy) pattern takes shape.