People use mathematics to model real-life situations. Such modeling is guided by analogical alignment between semantic and mathematical relations (Bassok, Chase, & Martin, 1998). For example, when college students solve or construct word problems, they tend to add taxonomically related objects (tulips + daffodils) and divide thematically related objects (tulips/vases) but not vice versa. We used event-related potentials (ERP's) to examine whether such alignments can be detected during comprehension of addition and division mathematical statements. For addition statements, we found reliable ERP effects characteristic to semantic anomalies in sentences: Statements which violated semantic alignments (e.g. 4 tulips + 2 vases) produced a reliable increase in N400 amplitude relative to statements that preserved semantic alignments (e.g. 4 tulips + 2 roses). For divsion statements, we found differences in N400 effects among division problem-solvers that were strongly correlated with participants' problem-solving strategies. Participants who produced responses that integrated the mathematic and semantic componenets of the task (e.g. 8 tulips/2 vases = 4 tulips per vase) showed increased N400 amplitude to statements violating semantic alignment (e.g. 8 tulips / 2 roses). Other participants performed the correct mathematical operation on the numbers but labeled their answer with a term corresponding to the conceptual integration of the word pair, for example 8 tulips/2 vases = 4 floral items. These participants did not show increased N400 amplitude in response to statements violating semantic alignment (e.g. 8 tulips / 2 roses). These results are discussed with respect to both semantic alignment theory and the nature of the N400 effect. .