The article proposes a model for evaluating budget reforms that combines insights from budgeting, policy implementation, and system-dynamics literatures. System-dynamics modeling combines both quantitative and qualitative research techniques to provide a new framework for applied research; its use is illustrated using performance budgeting as an example. Applied to the implementation of Florida's performance-based program budget, the model identifies actions in the short run that will increase the reform's likelihood of success: providing clear communications; facilitative budget and accounting routines; reliable performance information. The model also identifies critical legislative behaviors that influence executive implementation: how the legislature in the long-run uses performance information to inform resource allocation and how it applies incentives or sanctions to programs that achieve or fail to achieve their performance standards. The legislature has the opportunity to use program reviews prepared by legislative staff to invigorate the executive branch's resolve to continue implementing the reform.Throughout the last century, state and local governments were laboratories for budget reform. Many reforms were heralded but never implemented; others were implemented initially but did not survive changes in administration. Others at least partially succeeded, only to be followed by still more reforms. The result is a landscape of hybrid budgets in which fragments of the latest budget reform are overlaid and integrated with the most useful parts of previous budget reforms.In 1994, the Florida legislature passed the Government Performance and Accountability Act (chapter 94-249, FS), requiring a statewide, phased-in conversion to a budgeting approach it called "performance-based program budgeting" (PB 2 ). Because Florida is one of only two states that apply budgetary incentives and disincentives for performance results (Melkers and Willoughby 1998), studying the state's experience should provide valuable insights. Judged against the prescriptions of rational budgeting theory, performance-based program budgeting would be given high marks as a good budget reform. PB 2 requires government spending to be classified by program; programs must have missions and objectives; and input, output, and