This paper explores the nature and centrality of maintenance and repair ('M&R') work in the extension and sustainability of ICT infrastructure in the global South. Drawing from pragmatist traditions in CSCW and the social sciences at large, we develop a concept of 'repair worlds' intended to map the varieties and effects of such maintenance and repair activities. Empirically, our analysis builds on ethnographic fieldwork into local practices of maintenance and repair that have accompanied and supported the extension of mobile phone and computing infrastructure in the Kavango region of northeastern Namibia.