This paper deals with the role of the lexicon versus the syntax in event structure by examining particle verb formation in German. There are two types of particles in German: Delimiting particles, which derive accomplishments or activities from activity base verbs, and nondelimiting ones, which leave the aspectual class of the base verb (activity) unchanged. A theory such as Ritter & Rosen (1998, to appear), which explicitly represents event structure in the syntax (e.g., through an FF-delimitation) is not able to account for the German facts, as it cannot explain the uniform morphosyntactic behavior of all particles. An analysis which combines syntactic structure (VP-shells, following Hale & Keyser (1994), Chomsky (1995)) and lexical features is adapted. It treats particles as heads of an empty PP in the lower VP. Delimiting particles are distinguished from nondelimiting ones through a lexical feature [+delim]. This analysis is also successful in providing homogeneous case-marking for all internal arguments. It questions Ritter & Rosen's purely syntactic analysis of event structure, where delimitation is assumed to be a grammatical primitive.