markdownabstractIndustrial symbiosis is a process in which firms in regional industrial systems engage in the exchange of by-products and sharing of utilities and services in order to improve their environmental and economic performance. Industrial symbiosis has a prominent social dimension. To capture the social dimension concepts from the social sciences have been introduced to the field. This thesis makes one of the first attempts to bring these together in an integrated conceptual framework. The social dimension of industrial symbiosis refers specifically to the institutional capacity of actors to coordinate their actions and interactions towards industrial symbiosis. In the thesis, the implications of the conceptual framework are tested through empirical studies, the results of which are used to present an improved framework in the conclusions. At the core of the improved framework is a two-phases model of the process through which actors build institutional capacity for industrial symbiosis. In the first phase, a common ground emerges between independent projects, that are started for disparate purposes, but are also potential building blocks for industrial symbiosis. The presence of bridging actors ensures that the emergent common ground is recognized and translated to a shared vision. With the development of the vision, the building blocks are assembled into a larger collaborative process. This triggers the second phase, in which the collaborative process unfolds as an assemblage of interrelated projects, aimed at the implementation of industrial symbiosis. The thesis also makes methodological contributions. Throughout the thesis, different methods, techniques and tools for longitudinal research are introduced as part of an innovative methodology called Event Sequence Analysis.