Amicrocomputer system for the layout and design of polyethylene intermediate‐pressure gas networks is presented. The procedure is designed for use on an IBM‐XT compatible machine with an EGA card that has full interactive graphical features. The program performs hydraulic design calculations and cost analyses of networks with layouts obtained using the Minimum Spanning Tree algorithm. Procedures derived from properties of Steiner trees and a simple “expert system” have been incorporated in the program to overcome the rectilinear requirements of pipeline layout. Rail‐and stream‐crossing considerations are also embedded in the layout procedures. The system is demonstrated by application to an actual natural gas distribution sys