Being truthful is a virtue, in life as in public health. While it is never ethical to intentionally misrepresent or mislead, how should public-health professionals convey truthful messages that achieve a desired public-health outcome? In this lecture, Harvey Fineberg considers five dilemmas confronting public-health messaging, specifically when: (1) evidence is incomplete; (2) new knowledge prompts a change in policy or practice; (3) framing messages are used to promote desired behavior; (4) shaping messages are required to suit audiences; and (5) using generalized vs. targeted health communication. Fineberg says public trust depends on a shared confidence in the expertise and candor of public-health professionals. Making near-term decisions that preserve this long-term goal is thus one of the persistent challenges facing public-health administration. Introduction by Lothar H. Wieler, Speaker, Digital Health Cluster; Chair, Digital Global Public Health, Hasso-Plattner-Institut, Universität Potsdam; former President, Robert Koch Institute