The functional primacy of syntactic over semantic processes was put to test in an auditory event-related brain potentials study using sentences in which the final words were semantically and/or syntactically incongruent with the prior context. Crucially, these words encoded the syntactically relevant word category information in the suffix, available only after the word stem which carried the semantic information. Semantic violations elicited an N400 and syntactic violations a biphasic LAN-P600 pattern. Words that were semantically and syntactically incongruent with the context evoked a biphasic LAN-P600 ERP pattern, but no N400. The similarity of the ERP pattern for the pure syntactic and the double violation condition provides strong evidence for a functional primacy of initial syntactic over lexical-semantic processes.