The design and development of educational technologies is a complex, interdisciplinary endeavor. Learning science research reveals principles of learning and instruction, and advances in computer science implement these principles in innovative technologies. This chapter promotes a complementary discipline—human systems engineering or “user science”—that emphasizes designing with human users' goals, needs, capabilities, and limitations in mind. Systematic and iterative human systems engineering should contribute to educational technologies that are more functional, usable, desirable, and ultimately more effective. The authors overview key human systems engineering principles (e.g., usability and user experience) and methods (e.g., cognitive task analysis, contextual inquiry, heuristic evaluation, and participatory design), and then consider example applications from research on automated writing evaluation technologies. The chapter concludes with broad research questions posed to researchers, developers, and educators in the field of educational technology.