Event-related potentials were recorded in a sentence reading paradigm. Sentences were either terminated by a semantically and grammatically appropriate word (word from a different grammatical class syntactic error), a semantically inappropriate word (semantic error) or a semantically appropriate word with a wrong case inflection (morphosyntactic error). For all three types of errors the event-related potential was characterized by a negativity in the 250-600 ms range (N400). The possible implications of these findings for models of sentence processing are discussed. It is concluded that the results strongly support interactive models of sentence processing.