After a quick survey of the famous pioneers of human movement analysis and the actual needs in different domains, this book presents the main types of systems available on the market (with the pros and cons), and then details the most widely used: the optoelectronic systems using passive markers. The theoretical background for joint kinematics calculation is explained, specifying the international standardization for parameters reports. One chapter is dedicated to measurement errors and their management, followed by several applications, mostly in the clinical field.