Hagoort [1] suggested that the posterior temporal cortex is involved in the retrieval of lexical frames that form building blocks for syntactic unification, supported by the inferior frontal gyrus (IFG). FMRI results support the role of the IFG in the unification operations that are performed at the structural/syntactic [2] and conceptual/ semantic levels [3]. While these studies tackle the unification operations within linguistic components, in the present event-related FMRI study we investigated the interplay between sentence-level semantics and syntax by adapting an EEG comprehension paradigm [4]. The ERP results showed typical P600 and N400 effects, while their combined effect revealed an interaction expressed in the N400 component ([CB-SE] - [SY-CR] > 0). Although the N400 component was similar in the correct and syntactic conditions (SY  CR), the combined effect was significantly larger than the effect of semantic anomaly alone. In contrast, the size of the P600 effect was not affected by an additional semantic violation, suggesting an asymmetry between semantic and syntactic processing. In the current FMRI study we characterize this asymmetry by means of a 2x2 experimental design included the conditions: correct (CR), syntactic (SY), semantic (SE), and combined (CB) anomalies. Standard SPM procedures were used for analysis and only clusters significant at P <.05 family-wise error corrected are reported. The main effect of semantic anomaly ([CB+SE] > [SY+CR]) yielded activation in the anterior IFG (BA 45/47). The opposite contrast revealed the theory-ofmind and default-mode network. The main effect of syntactically correct sentences ([SE+CR] > [CB+SY]), showed significant activation in the IFG (BA 44/45), including the mid-anterior insula extending into the superior temporal poles (BA 22/38). In addition, significant effects were observed in medial prefrontal/ anterior cingulate cortex, posterior middle and superior temporal regions (BA 21/22), and the basal ganglia. The reverse contrast yielded activations in the MFG (BA 9/46), the inferior parietal region (BA 39/40), precuneus and the posterior cingulate region. The only region that showed a significant interaction ([CBSE]  [SYCR] > 0) was the left temporo-parietal region (BA 22/39/40). In summary, the results show that the IFG is involved in unification during comprehension. The effect of semantic anomaly and its implied unification load engages the anterior IFG while the effect of syntactic anomaly and its implied unification failure engages MFG. Finally, the results suggest that the syntax of gender agreement interacts with sentence-level semantics in the left temporo-parietal region. [1] Hagoort, P. (2005). On Broca, brain, and binding: A new framework. TICS, 9, 416-423. [2] Snijders, T. M., Vosse, T., Kempen, G., Van Berkum, J. J. A., Petersson, K. M., Hagoort, P. (2009). Retrieval and unification of syntactic structure in sentence comprehension: An fMRI study using word-category ambiguity. Cerebral Cortex, 19, 1493-1503. doi:10.1093/ cercor/bhn187. [3] Hagoort, P., Hald, L., Baastiansen, M., Petersson, K.M. (2004). Integration of word meaning and world knowledge in language comprehension. Science 304, 438-441. [4] Hagoort, P. (2003). Interplay between syntax and semantics during sentence comprehension: ERP effects of combining syntactic and semantic violations. Journal of Cognitive Neuroscience, 15, 883- 899.