Five leading fourth grade Social Studies textbooks were analyzed to determine their overall readability and comprehensibility and to determine the extent to which provisions for dealing with students' prior knowledge were included in Teacher Editions. Two readability formulae were used. The Fry Graph Analysis indicated that texts were written at the appropriate grade level; however, the Singer Inventory, which examines factors closely related to comprehensibility, indicated that the texts were not well-organized, and they contained a large number of disparate concepts that were inadequately explained. In the analysis of the Teacher Editions, it was determined that students' prior knowledge was rarely used and acknowledged as a factor for learning. The analysis of suggestions within the Teacher Editions for using students' prior knowledge to expedite learning was divided into three parts: analysis of suggestions for dealing with content; instructional suggestions and vocabulary suggestions. Few recommendations were offered in any of these categories. The most frequent suggestion in the content category was the inclusion of background facts that were related to the content of the text. The most frequent suggestion in the instruction category was the recommendation that teachers tell students to "look at" illustrations (maps, charts) before reading. In the vocabulary category, it was determined that no suggestions were offered 74% of the time for the words that the authors had selected as important words. The final part of the study was an analysis of three leading basal readers to determine the ways in which prior knowledge was discussed in relation to Social Studies selections (within the basal) and narrative selections. There were few differences between narrative selections and Social Studies selections. Prior knowledge was acknowledged and used as a critical feature in comprehending and learning from text. The five Social Studies textbooks were compared with the basals, and it was determined that the basals included far more provisions for dealing with prior knowledge in each of the three categories than did the Social Studies textbooks. In the basal readers, teachers were encouraged to ask children to personalize their prior knowledge to serve as a framework for interpreting new information contained in the text. New vocabulary words were encouraged to be taught in relation to prior knowledge. The overall results of the study indicated that Social Studies textbook writers need to examine the ways in which students' prior knowledge can be used by teachers to help students learn from text.