Computerized and three-dimensional gait analysis systems supply quantitative data about kinematics and kinetics of the gait unlike the visual gait analysis. The results can be utilized for diagnostics, rehabilitation planning and evaluation, during prosthetic and orthotic design, tuning and evaluation. Data obtained being numerical and objective are the two other major advantages of gait analysis systems. However, it is important to consider the methods of obtaining direct measured data and computed quantities presented as the results of gait analysis system. In this review the methods of data collection and processing, and finally computation of the results are presented from an engineering point of view.