This paper discusses the use of a computerised model for the allocation of a contract for operational work. The contract covers a defined period—normally two or three years, applies to one area or one Region of British Gas and is shared amongst many contractors. Millions of pounds are spent on all these contracts each year. The model was transferred from a mainframe to a microcomputer. The factors influencing this decision are presented, examined and seen to have aspects which apply generally. The study is used as an illustration of the problem of choosing between a mainframe and a microcomputer for an application.