The paper reports the basis for a cognitive walkthrough method to support the evaluation of multimedia (MM) expository presentations (e.g. ‘how to do it’ type tasks). The walkthrough is founded upon an analysis of the cognitive processes and representations formed by the comprehension of an MM presentation. Issues include evaluation of attention, topic focus and information types. The walkthrough provides a series of guidelines for evaluation based on these cognitive models, such as the use of media, scripting and presentation techniques. The value of the guidelines is validated by several empirical studies. An eye tracking study is reported, providing evidence as to how visual attention responds to MM materials. A series of comprehension studies then investigate the effectiveness of a presentation before and after our guidelines were applied. The paper is illustrated with an example evaluation and studies of a commercially produced CD-ROM MM presentation ‘The Biology of Cancer’.