A computer program written in Turbo C is described, which uses the two-step mathematical procedure published recently (Rothe, G. M., Electrophoresis 1988, 9, 307-316) to evaluate the molecular mass, Stokes' radius, spherical radius, and frictional coefficient of nondenatured proteins. The program runs on any IBM-PC or 100% compatible IBM-PC, provided the disk operating system MS-DOS or PC-DOS 3.0 or later has been installed. Functions that are permanently in use are accessible by menu. Storage and loading of data from disk and help instructions can be called by use of function keys. The program provides several tables into which inserted and calculated data is automatically integrated. Each table can be printed out, provided a printer with IBM character set is connected to the computer.