AbstractAn investigation was undertaken in late 1982/early 1983 into the computing needs of operational research workers in British Gas. The approach was first to draw up a specification of O.R.'s computing needs in terms of service levels, provision of hardware and software. Alternative options for meeting this specification were then costed out. Options examined included an interactive service on the mainframe computer, use of a minicomputer, and the use of micros plus mainframe interactive service. The results are given in the paper for various sizes of O.R. group, together with the results of sensitivity exercises.