The purpose of this study was to objectively evaluate the fit of sockets for trans-tibial stumps in order to establish a guideline for use in the automated production of prosthetic sockets. Subjects were 24 trans-tibial amputees. Using a CAD/CAM system, 11 parameters regarding the 3D shape of the stumps and the sockets were objectively evaluated. A correlation was found between the activity level and the upper and lower volumes of the socket, and between the cause of amputation and the upper volume of the socket. It was considered desirable to make the lower part of the socket looser for patients with lower activity levels, to make the upper part tighter for patients with higher activity levels, and to make the upper part looser for amputation patients with peripheral circulatory diseases.