As the marketing literature increasingly construes markets as malleable entities, research studies of ‘marketshaping’strategies have gained increasing attention in recent years. Those are proactive, deliberate initiativeswhich a firm takes with the aim of re-shaping an operating environment comprising direct customers, customers'customers, and other actors such as its competitors. Our study derives a theoretical framework for marketshapingfrom the existing literature and an in-depth case study of one market-leading firm in the steel industry,which has been working actively in the shaping of a market. Analysis of the responses of a range of experiencedexecutive staff to unstructured and semi-structured interviews shows, among other things, that in order to shapethe market, the firm performed many individual and aggregated activities at three levels of influence – system,market offer and technology – with various actors in the market in focus. These findings are the basis of aproposed activity framework for the proactive shaping of a market: that is, what firms can do in order to shapean existing market, drive growth and create sustainable competitive advantage.