Two representative samples of expository prose from sixth grade textbooks (one in science and one in social studies) were analyzed for clarity of explanation. Four text criteria were applied to the analyses: structure, unity, coherence, and audience appropriateness. The results of the analysis suggested that many children's textbooks are not clearly written. It was proposed that the procedures commonly used by authors to make texts easier to read (shorter sentences, easier vocabulary, less detail, and use of condensed explanations of ideas) may instead cause the text to be even more difficult to comprehend. The effect of poor quality text on how well children learn to read and comprehend text may also be very great. A third suggestion, based on these research results, is that poorly written texts may develop undesirable student attitudes toward reading texts. To combat these possible effects of poorly written texts, it was proposed that editors and publishers monitor textbook production more carefully, that teachers evaluate texts carefully and help students develop textbook reading skills, and that authors of textbooks pay closer attention to structure, coherence, unity, and audience appropriateness. (The response of one of the publishers of the textbooks that were evaluated is attached and is followed by comments from the editor of this report series.) (RL)