A study examined 20 trade books (1964-1997) to evaluate their accuracy in depicting Native American peoples and cultures. The criteria embodied an authenticity guideline based upon the "Five Great Values": (1) generosity and sharing; (2) respect for elders and women; (3) getting along with nature; (4) individual freedom and leadership; and (5) courage. Results indicated that 60% of the books are at least satisfactory in their depictions but that bias and stereotyping still persist enough to recommend the use of the guideline as a tool to allow educators to confidently identify these problems in their instructional materials. Contains 3 tables of data, 15 references, and the Native Cultures Authenticity Guideline. (Author/BT)