World Bank Discussion Paper No. 363. Program-based approaches to providing development assistance, especially sector investment programs (SIPs), are receiving increased attention as donors and recipient countries search for effective instruments to foster sustainable development. A SIP is a long-term national program covering public expenditures in an entire sector, such as energy or telecommunications. This paper conveys the results of a World Bank task force assembled to examine the results of these programs. It describes the rationale and analytical basis for SIPs and the lessons learned through early implementation experience. The report argues that SIPs can have a greater development impact than free-standing projects because they holistically address the underlying conditions that may impede a project's effectiveness.