This paper introduces an evaluation tool prepared to examine the quality of visuals in course-books. The tool is based on Mayer's Cognitive Theory of Multimedia Learning (i.e. Generative Theory) and its principles regarding the correct use of illustrations within text. The reason to generate the tool, the development process along with the theoretical procedures followed, reliability studies and users' manual of the instrument are provided within the study. Includes appendix: Evaluation Scale for Visuals. (Contains 2 figures.)