The purpose of this study was to measure the influence of prior knowledge on reading comprehension. Twenty second-graders who were reading at, or not more than one year above, grade level were pretested to determine the extent of their prior knowledge about the topic they would be reading. Based on their pretest scores, the students were divided into two groups: one group had weak prior knowledge and the other had extensive prior knowledge of the topic. It was hypothesized that the group with more extensive prior knowledge would achieve better comprehension results. The study also investigated the possible influence of explicit and implicit questions on comprehension; half of the posttest questions were explicit and the others implicit. It was hypothesized that the implicit questions would be more difficult for both groups of students. Both hypotheses were substantiated. In addition, it was found that the ability to answer explicit questions did not differ significantly between the two groups of students, but those with greater prior knowledge were better at answering the implicit questions. (Author/MAI)