Aspects of successful market transformation are investigated both theoretically and empirically. At the theoretical level, success factors for single promotion activities are first discussed and classified, then for market transformation as a whole the emphasis is laid on the interactions between actors. Combined Action-Flow graphs are introduced as a tool for visualising the interconnections. In the empirical section, European experience with market penetration of condensing boilers is analysed. Thereby, both international comparisons and detailed customer surveys for several promotion activities in one country are used to identify the role of actors' interaction and promotion design factors in addition to usually considered technical and economic factors.