Event-related brain potentials (ERPs) were used to investigate how and when a semantic factor (animacy) affects the early analysis of a difficult syntactic structure, namely, object relative sentences. We contrasted electrophysiological and behavioral responses to two object relative types that were syntactically and lexically identical and varied only in the order of the component animate and inanimate nouns [Inanimate (Animate) vs. Animate (Inanimate)]. ERPs were recorded from 40 subjects to each word of 30 I(A) and 30 A(I) sentences that occurred randomly among a set of various other sentence types read for comprehension. ERP effects to the early noun animacy manipulation were observed beginning with the initial noun and extending past the main clause verbs. We interpret the timing and multitude of electrophysiological effects, including the N400, P600, and left-anterior negativity, as evidence that both semantic and syntactic, and perhaps other types of information, are used early during structural analysis and message-level computations as needed for comprehension.