A study was conducted to determine whether students who mapped prior and post knowledge of a basal reading lesson would achieve higher scores on a comprehension test and write better summaries of those stories than would students who received traditional basal reading instruction. Subjects, 30 fifth grade students, participated in either a treatment or a control group condition. Subjects in both groups read the same six stories. The treatment group teacher identified key concepts from each story and mapped the students' prior knowledge before each reading. Then the students read to confirm the accuracy of their knowledge, clarify misinformation on their maps, and add new information. Next, they wrote story summaries and completed a comprehension test. Instruction for the control group students concentrated on vocabulary words, silent reading, oral discussion, and summary writing. Results showed that test scores of the treatment group students were markedly higher than those of the control condition students. No difference was found in the overall quality of the writing of the two groups. (FL)