In countries recovering from conflict, defence institutions may be particularly resistant to change, often because change would entail loss of political control or decreased access to wealth, including reduced ability to exploit natural resources. Although bilateral defence assistance has been a staple of international aid for decades, assistance to equip and train partner defence forces cannot be equated with defence sector reform. Such assistance may not address corruption, human rights abuses, or the likelihood of internal conflict in recipient countries, whereas the core principles of security sector (system) reform emphasize good governance, transparency, efficiency, fairness and equity in recruiting and promotion, accountable and sustainable financing, respect for human rights, and local ownership based on democratic norms. Failure to reform the defence sector in broad terms-including its governance and oversight-will likely impair a country’s ability to build transparent, accountable, and efficient public institutions in general, and may also interfere with the larger economic recovery or development process. This practice note highlights good and bad practice and lessons learned regarding the design and implementation of defence sector reform programming.