This research involves the development of an on-shoe device that can be used for continuous and real-time monitoring of gait. This work involves the design of an instrumented insole and a removable instrumented shoe attachment, which will send data wirelessly, providing information about the three-dimensional motion, position, and pressure distribution of the foot. Algorithms will be developed to analyze the data in real-time, and results will be validated by comparison with data from a commercial optical gait analysis system at the Massachusetts General Hospital (MGH) BioMotion Lab. A small clinical study using this device will be carried out at MGH investigating the effects of physical therapy on subjects with Parkinsonís disease. Finally, real-time feedback methods will be developed in order to investigate the feasibility and benefits of using the continuous monitoring of gait for physical therapy and rehabilitation.