This report documents internal details of Industrial SICStus Prolog, developed at the Logic Programming Laboratory of SICS. The development was funded by Ericsson Telecomm AB, NobelTech Systems AB, Infologics AB and Televerket under the IT4-program. The Implementation was done on Sun-3 and Sun-4 workstations. It has proved portable to a wide range of byte-addressed 32-bit computers running Berkeley Unix.