An important challenge for the research on post-socialist big cities is to identify the mechanisms of their uncontrolled urban space growth. This analysis is focused on the built-up urban space affected by transformations from a centrally planned to a market-based economy. Post-socialist changes in Bucharest are clearly reflected in the dynamics of built-up space. Land cover dynamics were evaluated using spectral mixture analysis of Landsat 5 TM (Thematic Mapper) data to map percent impervious surface area in 1988 and 2010. Change analysis reveals (1) a decrease of built space in central and peri-central areas of Bucharest, (2) an expansion of new residential areas to the south, (3) land fragmentation to the east and southeast, (4) a mixture of densities to the north, and (5) the role of the ring road in spurring recent development. A key challenge facing Bucharest is the disposition and repurposing of the lands covered by old large housing estates and shuttered heavy industries.