Developmental trends in the effects of expectations regarding agent/action matches on judgments of sentence acceptability were investigated. Five sentences reflected expected relations ("harmonious") and five contradicted them ("contrary"). Twelve subjects each were in grades 4 through 8 during year 1; the same 60 subjects participated during year 2. Significant main effects were: expectation, with more harmonious sentences accepted; year, with the mean number of sentences accepted higher in year 1; and group, with the two older groups accepting fewer items. The group by expectation interaction was also significant: means of the three younger groups on harmonious sentences were higher than all other means. Changes in metalinguistic processes in evaluating sentence acceptability are suggested. (Author/CLK)