Korea has been leading the world in broadband Internet access services since 1999. Based on an in-depth case analysis of the penetration of asymmetric digital subscriber line (ADSL) in Korea, the present study explores the patterns of decision making and interactions among key innovation actors, such as the government, Internet service providers, equipment providers, and content providers, using a conceptual framework wherein models of innovation systems and decision making under uncertainty are combined. The results revealed that the Korean government played a pivotal role in the creation of the ADSL-based Internet service market by providing a strong vision for this emerging service, building a coalition among various key actors, and stimulating initial market needs and supply of necessary equipment during the early period of higher uncertainty. As the level of uncertainty decreased with market evolution, however, the role of industrial actors and their market competition became more important to the rapid growth of the ADSL market. Based on these findings, policy and managerial implications are proposed. (C) 2007 Elsevier Ltd. All rights reserved.