Cognitive load theory is a learning and instruction theory that describes instructional design implications of human cognitive architecture outlined in the previous chapter. Based on these theoretically and empirically established instructional consequences (usually referred to as cognitive load effects or principles), the theory makes specific prescriptions on managing cognitive load in learning and instruction. The theory distinguishes several different types or sources of cognitive load (e.g., effective and ineffective load; intrinsic, extraneous, and germane load) that are associated with different instructional implications and cognitive load effects. This chapter analyzes cognitive load factors that could potentially influence efficiency of interactive multimedia applications (e.g., levels of element interactivity, spatial and temporal configurations of instructional presentations, redundant representational formats, levels of learner prior experience in a task domain). Basic assumptions of cognitive theory of multimedia learning are discussed. The chapter starts with the description of the sources of cognitive load followed by an overview of the major cognitive load effects.