In the interest of making aid effective, donors are increasingly stressing the importance of a good public financial management (PFM) system in partner countries. The budget process is a part of the PFM system which is both very crucial to good development outcomes, and a process vulnerable to corruption. These issue pages collect evidence and knowledge in the area of corruption in the budget process which is operationally relevant for staff in international development agencies. What is budgetary corruption, how may it be detected and what should the policy responses be?