Slums are informal housing settlements commonly found in urban areas of developing countries which are characterised by poor shelter, low service provision and lacking in security of tenure. Slums are growing and new slums are forming. The international development community has been actively working to improve the living conditions of slum-dwellers and to reduce poverty via slum upgrading methods. There are various slum upgrading delivery models and approaches to tackle the urbanisation of poverty in developing countries. Many adaptive and proactive measures have been implemented through a variety of slum upgrading initiatives and partnerships; however there has been limited investigation of the longer term sustainability of such interventions. This research follows a qualitative methodology to investigate the sustainability of differing slum upgrading interventions. Four case studies have been examined; two in Kenya and two in India, demonstrating a range of physical upgrading approaches. Alternative slum upgrading delivery models have been selected covering housing rehabilitation and in-situ water and sanitation upgrading and demonstrating top-down and bottom-up approaches. The case studies are of varying ages and were implemented via partnerships with differing agents including government, NGO, CBO, private developer and donors. The influence and design of the delivery model upon the upgrading sustainability has been assessed via stakeholder perception during extensive fieldwork. The data gathered has been analysed according to four key themes; status of life for slum-dwellers today, perception of upgrading success, institutional reform from external factors and development aspirations. Data was gathered via semi-structured interviews with slum-dwellers and project stakeholders using a ground-level methodology that enabled the capture of personal and honest accounts. Analysis of the data has found that there are many misconceptions around slums which can affect the sustainability of measures to upgrade informal settlements. The way that international development organisations and westerners view slums is often very particular and not always resonant with the way that slum-dwellers view their living situation. Priorities for development are not always consistent across stakeholders. For sustainability, any slum upgrading activity must be sensitive to the situation of an individual community and culture, and not assume that the residents are unhappy living in desperate poverty, as it has been shown, many choose to reside in a slum. Slums may be dirty, poorly serviced and overcrowded but are also places of great human energy, community spirit, kindness, hard-working, creative and happy places that many consider home.