A small boundary element computer program, KYOKAI. 3D, is presented. The program package is dedicated to the numerical solution of linear potential problems and elasticity in three dimensions. Boundary element mesh is automatically generated by preprocessor via an interactive standard graphic terminal. Constant boundary elements are used for the discretization of boundary integral equations. Calculated equipotential lines and traction contours are plotted on arbitrary solid surfaces of the model by postprocessor. The KYOKAI. 3D aimes at providing engineers who have little knowledge about both three-dimensional modelling and boundary element method. The user is conducted by easily comprehensive, interrogative commands. Typical examples are demonstrated to access the versatility of this turn-key system.