With the Sustainable Development Goals (SDGs) now agreed, the real test of their success lies in their implementation. Over half the world's population now live in cities and by 2050 this will rise to two-thirds. Most of this growth will take place in developing countries due to rising migration from rural areas. How countries manage this growing urbanisation over the next 15 years will define governments' ability to achieve most of the the SDGs. This report uses Mumbai as an example for an analysis of performance over time on three SDG targets at slum and settlement levels and provides recommendations for early action on SDG implementation in cities.