This reflective paper surveys the lessons learnt and challenges faced by the Mistra Urban Futures (MUF) research centre and its research platforms in Sweden, the UK, South Africa and Kenya in developing and deploying different forms of transdisciplinary co-production of knowledge. Considerable experience with a distinctive portfolio of such methods has been gained and reflective evaluation is now under way. While it is important to understand the local context within which each method has evolved, we seek to explain the potential for adaptation in diverse contexts so that such knowledge co-production methods can be more widely utilized. Furthermore, the current phase of MUF's work is undertaking innovative comparative transdisciplinary co-production research across its research platforms. Since the specific local projects differ, systematic thematic comparison requires great care and methodological rigour. Transdisciplinary co-production is inherently complex, time consuming and often unpredictable in terms of outcomes, and these challenges are intensified when it is undertaken comparatively. Keywords comparative urban research / co-production / Mistra Urban Futures / transdisciplinarity / transdisciplinary urban co-production I. InTroducTIon: From unIlocAl To compArATIve TrAnsdIscIplInAry co-producTIon oF Knowledge Co-production (also known as co-creation or co-design (1)) as an approach has evolved since the 1980s. The objective has been to bring different stakeholder groups together in an attempt to overcome often-longstanding antagonisms and wide asymmetries of power by working or researching together to improve outcomes, whether of services or research, and their legitimacy. (2) Essentially, the many modes of co-production constitute more sustained and coherent forms of the diverse participatory research and consultation methods developed to engage with local communities, research subjects, or the intended beneficiaries of development or service investments. There is no clear boundary between co-production and participation-when the intention is to increase diverse stakeholders' power. Indeed, for instance, participatory budgeting, of the kind initiated in Porto Alegre (Brazil) and subsequently applied in diverse cities, (3) has many attributes of co-production. david simon is director of mistra urban Futures and professor of development geography, royal Holloway, university of london.