The present study used latent semantic analysis (LSA) to analyze verbal protocols that were collected while participants read expository passages. In the study, participants were asked to type their thoughts after reading each sentence of 2 scientific texts. The semantic similarity between the protocols and the current sentence and prior causal sentences was computed using LSA. The magnitude of the similarity, as expressed by LSA-generated cosines, predicted performance on comprehension questions and the Nelson-Denny test of comprehension. The results were discussed in the context of previous research and test development.