In 1998, the Riksdag decided on certain amendments to the Act (1988:1387) on Government Borrowing and Debt Management. Pursuant to the new rules, the government was to establish fixed guidelines for the management of the central government debt. The guidelines follow proposals from the Swedish National Debt Office. This year the government has instructed the Debt Office to develop simulation methods for analysing the costs and risks associated with alternative debt structures. The result of this assignment is presented in this memorandum in the form of a concrete proposal for a model for analysing the structure of the central government debt and for drawing up proposals for guidelines. This memorandum also includes a discussion of what definitions of cost and risk should be used as a basis for making decisions on the structure of the debt.