Classroom teachers frequently express concern that textbooks and other curriculum materials are too difficult for their students. The objectives of this investigation were to develop a method for scoring the Level of Abstraction (LOA) of science reading material, and explore its relationship with certain other known methods for assessing curriculum materials (passage readability level, student cloze score, and teacher prediction of students' level of comprehension). Also examined were relationships between students' cloze scores and passage readability levels. The study was based upon nine passages taken from life, earth, and physical science textbooks written at three different levels. Non-significant correlations were found between: (1) passage LOA and passage readability; (2) student cloze scores and passage LOA; (3) passage LOA and teacher prediction of student success; and (4) student cloze scores and passage readability level. However, the consistent and high, but non-significant correlations between LOA and cloze scores combined with the fact that the LOA is based upon deep structure rather than surface structure of written material indicate the importance of further investigation of the LOA in its relationship to student comprehension of written material. (Author/TW)