This paper gives an account of the event and argument structure of past participles, and the linking between argument structure and valence structure. It further accounts for how participles form perfect and passive constructions with auxiliaries. We assume that the same participle form is used in both types of construction. Our claim is that the valence structure of a past participle is predictable from its semantic type, and that the valence structure predicts which auxiliary a past participle combines with in perfect constructions and whether the past participle may occur in passive constructions. Our approach sets itself apart from similar approaches, cf. e.g. Heinz & Matiasek (1994), Kathol (1994), Pollard (1994) and Müller (2003), with its strong emphasis on semantics.