In their self-understanding, expert committees solely draw on scientific knowledge to provide policy advice. However, we try to show, first, on the basis of material related to the German Radiation Protection Commission that much of their work consists in active model building. Second, expert advice is judged by criteria that diverge from standards used for judging epistemic research. In particular, the commitment to generality or universality is replaced by the criterion of specificity, and the value of precision gives way to (...) epistemic robustness. Third, non-epistemic considerations are included in the reasoning—albeit hesitantly. Manageability and social robustness, understood as compatibility with widespread value attitudes in society, affect the content of the recommendations. (shrink)