Abstract: A joint range of motion evaluation system includes a three-dimensional orientation device which generates Euler angle (azimuth, elevation, roll) data closely corresponding to the permitted angular ranges of motion for many joints in a patient's body. Thus, the system collects angular data corresponding to the same angular movements experienced through the joint to provide greater information with regard to its actual movement. This information is particularly useful in detecting abnormalities and disabilities of movement and in designing and monitoring patient rehabilitation. Specific positional data with respect to specific points on the patient's joint or other surrounding anatomy is not utilized.