R3D - Field is a three dimensional electrostatic field calculating program for arbitrary electrode configuration with well defined boundary conditions and three dimensional dielectrics. Many advanced electrical devices can not be simplified to a two dimensional problem, this program permits calculating electrostatic field problems where only three dimensions can properly describe the actual physical conditions. It also permits adding small defects into a two dimensional problem, in the third dimension, thus permitting the calculation of physical tolerances needed in the construction process to ensure satisfactory operation. The program can handle a large number of different dielectric constants so that variations in fields with slight changes in dielectric constants can also be studied. Based on a finite difference method in three dimensions. The program calculates the three dimensional electric field on a lattice with fixed, wrap - around or reflective boundary conditions. Two dimensional planes, from the three dimensional volume, can be shown with contour plots of equipotentials and lines of force. The program is interactively command driven where parameters are entered by the user.