Sentence comprehension abilities of adults ranging in age from 18 to 80 years were compared as they enacted, through an object-manipulation task, the meanings of spoken sentences containing relative clauses. A decline in performance was observed beginning with subjects in their 60s. Those in their 70s not only erred more frequently than younger subjects, but also made errors of a more serious nature. Great variability was observed within age groups, some of which was accounted for by vocabulary and digit span scores and by educational level. Even after adjustment for the relevant variables, scores for the older groups were bimodally distributed. These results are discussed in terms of cognitive factors underlying sentence comprehension.