Cognitive processing limitations restrict the number of complex information items held and processed in human working memory. To overcome such limitations, a verbal working memory channel is used to construct an if-then proposition representation of facts and a visual working memory channel is used to construct a visual imagery of geometric spatial information. Recent findings suggest that these two channels augment each other in enhancing cognitive processing, thereby increasing comprehension and retention. Multimedia computing provides a variety of information presentation modality combinations (i.e., text, pictures, narration, animation, and video). The fact that educators have observed that visuals enhance learning suggests that multimedia presentations should be superior to text-only and text with static pictures in facilitating optimal human information processing and, therefore, comprehension. This article reports the findings from a 3 (text-only, overhead slides, and multimedia presentation) 2 2 (high and low information complexity) factorial experiment. Subjects read a text script, viewed an acetate overhead slide presentation, or viewed a multimedia presentation depicting the greenhouse effect (low complexity) or photocopier operation (high complexity). Multimedia was superior to text-only and overhead slides for comprehension. Information complexity diminished comprehension and perceived presentation quality. Significant interactions indicated that multimedia was able to reduce the negative impact of information complexity on comprehension and increase the extent of sustained attention to the presentation. These findings suggest that multimedia presentations invoke the use of both the verbal and visual working memory channels resulting in a reduction of the cognitive load imposed by increased information complexity. Moreover, multimedia superiority in facilitating comprehension goes beyond its ability to increase sustained attention; the quality and effectiveness of information processing attained (i.e., use of verbal and visual working memory) is also significant.