This document discusses measuring engagement within educational multimedia environments and games using both covert and overt methods. It provides definitions of engagement in learning and gaming contexts. Various methods for measuring engagement are described, including observational analysis, physiological sensors, and subjective surveys/questionnaires. Specific examples are given around using physiological sensors like skin conductance and eye tracking to measure engagement levels during a Guitar Hero game. The goals of measuring engagement are to enable dynamic difficulty adjustment, expand learner demographics, and increase time on task.