Sanitation is often among the priority problems that slum dwellers identify through participatory planning methodologies. There are actions that communities themselves can take to address this, but NGOs like Practical Action can support them in terms of choice of technology, models for community management, and access to financing (including from the Local Authorities). From 2006-2009 we worked with 24 slum communities (21,500 people) across 4 towns in Bangladesh, Nepal and Sri Lanka, with sanitation being a focus of interventions in 2 of these towns. Our interventions proved sustainable, but relatively limited in scope. We are now working on scaling up those achievements to cover 6 towns and 78 slum communities. This paper highlights the methods we adopted, the achievements of the first phase of our work and the challenges in scaling up for city-wide impacts benefiting all the slum dwellers in the city.