This paper explores how knowledge systems can effectively harness science and technology (S&T) for sustainable development. The authors argue that successful systems for sustainability are more likely to be effective when they manage boundaries between knowledge and action in ways that enhance the salience, credibility, and legitimacy of the information they produce. Effective systems apply a variety of institutional mechanisms that facilitate communication, translation, and mediation across boundaries. The study draws on case studies from various sustainability issues, including agricultural productivity, aquifer depletion, ENSO forecasting, ocean fisheries, and transboundary air pollution. These cases highlight the importance of managing boundaries between knowledge and action, and the role of communication, translation, and mediation in achieving this. The authors identify three key functions that contribute to effective boundary management: communication, translation, and mediation. Communication is crucial for systems that mobilize knowledge seen as salient, credible, and legitimate in the world of action. Translation is necessary for linking knowledge to action, and mediation is essential for resolving conflicts among efforts to attain salience, credibility, and legitimacy. The study also identifies three institutional features that are characteristic of systems that effectively harness S&T for sustainability: treating boundary management seriously, dual accountability, and the use of boundary objects. These features are essential for building effective information flows and ensuring that the information produced is salient, credible, and legitimate. The authors conclude that building more effective knowledge systems for sustainability takes time and patience. Strategies to promote such systems require a sufficiently long-term perspective that takes account of the generally slow impact of ideas on practice, the need to learn from field experience, and the time scales involved in enhancing human and institutional capital necessary for doing all these things. A decade or more seems the minimal period over which efforts to harness S&T for sustainability should be planned, implemented, and evaluated.This paper explores how knowledge systems can effectively harness science and technology (S&T) for sustainable development. The authors argue that successful systems for sustainability are more likely to be effective when they manage boundaries between knowledge and action in ways that enhance the salience, credibility, and legitimacy of the information they produce. Effective systems apply a variety of institutional mechanisms that facilitate communication, translation, and mediation across boundaries. The study draws on case studies from various sustainability issues, including agricultural productivity, aquifer depletion, ENSO forecasting, ocean fisheries, and transboundary air pollution. These cases highlight the importance of managing boundaries between knowledge and action, and the role of communication, translation, and mediation in achieving this. The authors identify three key functions that contribute to effective boundary management: communication, translation, and mediation. Communication is crucial for systems that mobilize knowledge seen as salient, credible, and legitimate in the world of action. Translation is necessary for linking knowledge to action, and mediation is essential for resolving conflicts among efforts to attain salience, credibility, and legitimacy. The study also identifies three institutional features that are characteristic of systems that effectively harness S&T for sustainability: treating boundary management seriously, dual accountability, and the use of boundary objects. These features are essential for building effective information flows and ensuring that the information produced is salient, credible, and legitimate. The authors conclude that building more effective knowledge systems for sustainability takes time and patience. Strategies to promote such systems require a sufficiently long-term perspective that takes account of the generally slow impact of ideas on practice, the need to learn from field experience, and the time scales involved in enhancing human and institutional capital necessary for doing all these things. A decade or more seems the minimal period over which efforts to harness S&T for sustainability should be planned, implemented, and evaluated.