Event-related potentials (ERPs) discriminated between contextually appropriate and inappropriate objects appearing in video film clips of common activities. Incongruent objects elicited a larger negative-going deflection, which was similar to the N400 component described previously in association with words and static pictures and which has been argued to reflect the integration of semantic information into a mental representation of the preceding context. The onset of this potential occurred shortly after object presentation, indicating that semantic integration is a rapid online component of real-world perception. In addition, the anomalies in movies evoked a large late positive potential at posterior regions, suggesting that in event perception, semantic incongruity may trigger cognitive processes other than those mediating pure semantic integration.