Since the opening of formerly closed markets in Eastern Europe and China in the early 1990s, numerous firms have sought to capture the growth opportunities prevailing in the virgin but institutionally distant business networks in these countries. I claim that the entry process into an institutionally distant business network has been realised when the entering firm has reached an insidership position in the network. To advance this idea, the thesis introduces the overlooked medium-sized multinational exporter (MME) and answers the following overarching research questions: (I) how do MMEs establish insidership positions in institutionally distant business networks, and (II) what critical abilities are developed by MMEs in the process of entering an institutionally distant business network? To answer these questions, qualitative and quantitative methods have sequentially been mixed to first give an in-depth understanding of the empirical field, and second to verify and generalise some of the most central tentative findings. Empirically, the study reports from a case study of eight firms in the Baltic Sea Region and from an on-site survey of 203 Swedish firms with experience of entries in Eastern Europe and/or China. Five individual essays are presented—all designed to reflect different aspects of the institutionally distant network entry process. The findings are condensed in the cover of the thesis, where it is claimed that an insidership position is reached through three main phases: the Scouting phase, the Qualifying phase and the Shielding phase. Furthermore, it is found that that the most critical abilities developed through the institutionally distant network entry process is local experience-based knowledge of high specificity. It is shown that previous experiences, generated in different business networks in mature markets, are not useful in the network entry process in immature markets. As a consequence, there is reason to believe that the entering firm needs to develop unlearning abilities to replace obsolete or misleading experience.