In the continuing search for ways to provide more effective aid, donors have committed themselves to making greater use of government systems and harmonising the way aid is delivered. Donors who agreed to the Paris Declaration on Aid Effectiveness in 2005 are free to choose their own modality, as long as they progressively shift towards those that use government systems in full. This working paper analyses the effectiveness of different aid modalities and the coordination mechanisms associated with programme-based approaches at the sector level. It draws from three case studies, covering the education sector in Tanzania, the water and sanitation sector in Uganda and the health sector in Mozambique, and also from the broader literature.