The environment for scientific research in public organisations is undergoing radical change, particularly with commercialisation pressures and blurring of the distinction between public and private research. The commercialisation pressures are reflected in government policy frameworks and institutional contexts for scientific work which are reconfiguring the context within which scientists work and raising questions about their identities, values, roles, motivations and careers. The changes represent a challenge to the traditional public good role of science and accompanying values. Based on an empirical study of a sample of research scientists from two public sector research organisations in Australia, this paper explores the interpretations and reactions of scientists to this changing environment. It shows that the changes have generated significant tensions between a set of norms entrenched in a traditional ethos of science and the emerging commercialisation imperatives that the scientists struggle to come to terms with or reconcile. (Contains 6 notes.)