Delik Hudalah is a PhD researcher at the Urban and Regional Studies Institute (URSI), University of Groningen and Urban Planning and Design Research Group (UPDRG), Institute of Technology Bandung; Faculty of Spatial Sciences, University of Groningen, PO Box 800, 9700 AV Groningen, Netherlands; email: d.hudalah@rug.nl. Haryo Winarso is a lecturer in the School of Architecture, Planning, and Policy Development, Institute of Technology Bandung, Labtek IXA Building, 2nd Floor, Jalan Ganesha no. 10 Bandung 40132, Indonesia: email: hwinarso@pl.itb. ac.id. Johan Woltjer is a lecturer in the Department of Planning, University of Groningen, PO Box 800, 9700 AV Groningen, Netherlands; email: j.woltjer@rug.nl. Paper submitted July 2007; revised paper received and accepted December 2007. Spatial transformation in peri-urban areas has provided an emerging picture of the growth of many metro- politan regions in developing countries. In this paper, we present a new perspective on this transformation from the viewpoint of the developing and transitional countries of East Asia, and suggest its potential implications for planning and governance. First, we reveal the uniqueness of peri-urbanisation in these countries in relation to its dependence on the metropolitan centres, capital accumulation and dynamic coexistence of urban and rural livelihoods. Although we acknowledge the growing contribution of peri- urban areas to regional economies, this is still at the expense of spatial cohesion, regional sustainability and quality of the physical environment. It is argued that these undesirable consequences have been a reflection of fragmented institutional landscapes, particularly at the regional level. In order to address this institutional fragmentation, we suggest a need to transform current domestic planning systems, strengthen collaborative approaches, promote innovative institution-building and consider rescaling of governance. Peri-urbanisation, which implies development of mixed land uses outside designated city boundaries, is a newly emerging challenge for the planning of East Asian cities and regions. Webster (2002) predicted that, over the next twenty years, around 200 million people will reside in the peri-urban areas of East Asian metropolitan regions – 40 per cent of the total urban population in these countries. Furthermore, the peri- urban areas of these countries, as in coastal China, may extend up to 300 kilometres from the major cities. This extension is much greater than that of African peri-urban areas, which usually fall within 30–50 kilometres beyond the existing city boundaries. In addition, peri-urbanisation around fast-growing large cities of East Asia is distinc- tive due to the rapid socio-economic transformation in such areas from rural towards urban livelihoods. At the same time, it is also characterised by the dynamic physical coexistence of rural and urban functions. There have been many empirical studies on peri-urbanisation, particularly in the developing world (Browder and Bohland, 1995; Simon et al., 2004; Webster, 2002). The implications for its planning and management have also been formulated (Brook and Dávila, 2000; McGregor et al., 2006; Allen, 2003; McGee, 1991). Indeed, the IDPR, 29 (4) 2007 Delik Hudalah, Haryo Winarso and Johan Woltjer Peri-urbanisation in East Asia A new challenge for planning? IDPR29_4_5_Hudalah.indd 503 28/2/08 08:09:42