AbstractA three-phase simulation system written in Pascal for use on microcomputers, minis and mainframes is presented. The advantages of the three-phase method are discussed, and the basis of the system explained. Although a traditional, textbook example is used to aid explanation and discussion, the system described in this paper has been used in real applications and in the teaching of simulation at Lancaster University and the London School of Economics. It also provides a basis for further research in simulation within both institutions.