Widespread enthusiasm for establishing scientific codes of conduct notwithstanding, the utility of such codes in influencing scientific practice is not self-evident. It largely depends on the implementation phase following their establishment-a phase which often receives little attention. The aim of this paper is to provide recommendations for guiding effective implementation through an assessment of one particular code of conduct in one particular institute. Based on a series of interviews held with researchers at the Department of Biotechnology of Delft University of Technology, this paper evaluates how the Netherlands Code of Conduct for Scientific Practice is received by those it is supposed to govern. While respondents agreed that discussion of the guiding principles of scientific conduct is called for, they did not consider the code as such to be a useful instrument. As a tool for the individual scientific practitioner, the code leaves a number of important questions unanswered in relation to visibility, enforcement, integration with daily practice and the distribution of responsibility. Recommendations are provided on the basis of these questions. There is more at stake than merely holding scientific practitioners to a proper exercise of their duties; implementation of scientific society