In adopting the Millennium Development Goals that address the most pressing development issues, countries pledged to halve the proportion of people without access to safe drinking water and basic sanitation. Yet, more than 1 billion people today lack safe drinking water, and some 2.6 billion - half of the developing world - lack improved sanitation. This publication reports on our progress towards the MDG goal of ensuring environmental sustainability. It seeks to encourage countries slow to meet the target to accelerate action, and highlights areas where efforts need to be strengthened in order to meet the goal.