The purpose of this study was to explore the influence of curricular organization on student cognitive load and student performance in online learning environments. The findings of this study contribute to the development of usable instruction design principles for online education. This research study used the lens of cognitive load theory to examine how online course organization affects student learning. A review of the literature included the elements of cognitive architecture that have been measured in prior studies, various methods in which cognitive load has been measured, and the basic requirements for measurement of cognitive load in instructional research. A traditional between-subjects design compared the effects of online course organization. Subjects were randomly divided into two groups in a computer-lab setting, each group engaged in online learning activities (reading, studying, completing assignments, taking assessments) in two separate online courses. Only the organization of the curriculum in the two courses was different. Results of the study generally indicated no significant difference between modular organization and functional organization in terms of the hypotheses. Under certain conditions, however, modular organization negatively impacted learners in terms of intrinsic load, time in content areas, and number of mouse clicks produced. Analysis of the two-way interaction effect of organization as the participants progressed through the course indicated a significant change over time. The implication of this study is that the rigid sequential structure of modular organization may benefit learners early in an online course by providing navigational cues, but becomes a burden over time as the learner becomes more adept at finding course content outside of the structure. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]