This dissertation evaluates the effects of relaxing the growth management tool known as the greenbelt policy in the Seoul Metropolitan Area (SMA) of South Korea. The policy effect is measured by employing a series of spatial and statistical analyses on four urban sprawl measurement criteria: 1) physical containment, 2) housing affordability, 3) community service provision costs, and 4) commuting costs. Based on the analyses, I concluded that as a result of the greenbelt relaxation, the SMA has lost substantial amounts of farmland, forestland, pastureland, and wetlands to development between 1990 and 2010. Despite the considerable land consumption, not much land fragmentation has occurred, meaning that the new developments took place near the existing built-up areas, especially near the satellite cities and New Towns outside the greenbelt. The greenbelt relaxation did contribute to mitigating the land price and property value increases throughout the SMA compared to the urban core in Seoul. Although the relaxation guided new developments inside the greenbelt and lowered the tax collection and expenditure outside the greenbelt, the community service costs are expected to be higher outside the greenbelt because more developments continued to happen outside the greenbelt regardless of the relaxation policy. The commuting destination analysis and the mode share statistics showed that the SMA as a whole is facing substantial transportation challenges in both cost and level of service.