This paper applies to the problem of urban poverty and particularly slums a conceptual framework based on systems theory. This conceptual framework provides a way of understanding the complexity and often-negative consequences of carefully articulated solutions to problems the are situated within extremely interrelated systems. Through a system theory approach, slums are characterised as a system- with particular components or features and the processes that perpetuate them. The framework also provides a conceptualization of sustainability that relates to the feedback characteristics of systems. According to the literal definition slums are 'sustainable', in that various characteristics operate in a mutually reinforcing process that maintains a cycle of poverty. Although slums are 'sustainable' they operate at a suboptimal level. This system needs to be changed so that the living standards of the urban poor are increased to a level considered adequate. In order to bring about appropriate and effective change to this suboptimal system, two key factors must be applied: Acknowledgement of the interdependence of systems before and after introducing change, and Applying solutions that create symbiotic benefits not just to the target system but the associated systems thus creating more robust and diverse relationships. Tenure security is identified as a key to slum improvement and poverty alleviation. Tenure security is a catalyst to a host of enabling opportunities for the urban poor. Within the systems framework, tenure security has the effect of generating a positive feedback system, whereby the processes within the slum system become mutually reinforcing, thereby lifting the living standards of the urban poor and in turn creating city wide improvements. Although this generates a positive feedback system that is inherently 'unsustainable' as it creates exponential growth, it is necessary to contribute to overall long term sustainability. Applying the literal definition of 'sustainable', 'to continue in a certain state, maintain at a constant level' then this level of sustainability must allow for a decent and adequate standard of living for all.