is thesis explores the overarching topic of the capacity of strategic urban development decisions and initiatives (including planning initiatives) to positively and powerfully influence the ability of a city to promote sustainable patterns of development. The work is presented in six scientific papers, the first four of which focus on the development of an inter-disciplinary conceptual framework and research methodology. The concept of Situations of Opportunity and its related Field of Options is proposed as a means to identify and analyse periods in the growth of cities when urbanisation can be more easily managed so as to promote sustainable development goals. Historical studies in the cities of Stockholm, Dar es Salaam and Curitiba are used to develop the methodology. Another paper looks ahead and refines the methodology in combination with future studies, presenting a research strategy that employs Situations of Opportunity as a means to identify and explore periods in the future urban growth with significant potential for change. Building on the method developed, the remaining two papers consider the social dimension of sustainable development and how it can be promoted in the urban context, during ongoing Situations of Opportunity. The concept of social sustainability is reviewed and discussed from two different disciplinary perspectives (urban development; companies and products), exploring commonalities and differences in approaches, and identifying core themes that cross disciplinary boundaries. A case study of Eastside, a brownfield redevelopment site in Birmingham (UK), reveals how the retention of established small food outlets can provide opportunities for promoting social sustainability goals in an urban regeneration area. Overall, this thesis provides a better understanding of how transformative change can happen in cities. The Situations of Opportunity concept developed here can be a helpful way to study strategic initiatives that promote sustainability in cities. / <p>QC 20101216</p>