This is a general information document describing the Hertfordshire Computer Managed Mathematics Project funded over a four-year period by the National Development Programme in Computer Assisted Learning. Its aims were to develop a two-year course for all-ability 11-to 13-year-old pupils and to implement a computer system to serve the course. This course would then be fully institutionalized within Hertfordshire and made available to other Local Education Authorities. The project has reached the point that development is giving way to production both for local and external use. Two courses are described in detail: (1) an individualized linear mathematics course divided into 25 topic-oriented modules to cover two years of instruction, and (2) a course of arithmetic tests covering the basic skills and concepts presented in the first course. Future concerns are added flexibility of routing and decentralization of control. (VT)