AbstractApplying the systems approach in practice requires compromises to be made in its ideals. This paper discusses this problem by examining two case studies of programme budgeting which can be seen to be an application of the systems approach; it attempts to expand the dimensions of budgeting away from an annual exercise based on functions to a process of medium-term planning based on programmes. The two case studies are the introduction and suspension of Planning-Programming-Budgeting-System (P.P.B.S.) in U.S. Federal Government and the various developments in the U.K. in the Public Expenditure Survey (P.E.S.C.). These provide illuminating contrasts in their intended scope and successful implementation. This contrasting experience suggests questions about systems theory. Should the essential characteristic of the systems approach be expansionism or adaptability? Can systems writing afford to ignore compromises necessary to achieve implementation, especially those made to satisfy political interests?