This document is the overall summary and synthesis of the first impact study of initiatives supported by UN-HABITAT’s Water and Sanitation Trust Fund (WSTF).The WSTF, which was established in 2003, aims to leverage new investment and ideas to expand the water and sanitation (WATSAN) service coverage for poor urban dwellers and help build momentum for achieving the MDGs. Its strategic plan for 2008 - 2012 envisions three key outcomes: • Increased institutional capacity in partner countries for pro-poor water and sanitation initiatives and policies with focus on gender equity, renewable energy and efficiency and environmental sustainability;• Increased flow of investment into water and sanitation sector catalysed by WSTF interventions; • Improved MDG monitoring mechanisms in place in partner countries, with improved benchmarking of water and sanitation service providers. The UN-HABITATWater, Sanitation and Infrastructure Branch (WSIB) seeks to maximise the impact of projects funded by the WSTF, and this impact study is the first of a series of impact assessments which will be undertaken over the next five years.