Subjects memorized sentences that contained a word with a synonym in English. There were large numbers of synonym substitution responses in recall (varying from 6.0% in Experiment I to 27.7% in Experiment III). Synonym substitution responses tended to be unidirectional and occurred with roughly equal frequency in abstract and concrete sentences. The results were interpreted as opposed to surface structure theories of sentence memory, since explanation in terms of word associations and sequential dependencies proved unsuccessful. The results were also taken to be opposed to image theories of sentence memory, since image theories predict few ff any synonym substitution responses for abstract sentences, while Experiment III found large numbers of synonym substitutions in both abstract and concrete sentences. The results support the position that memory for sentences is in terms of nonlinguistic, nonimage, abstract representations (ideas).