Hormesis has been defined as a dose-response relationship in which there is a stimulatory response at low doses, but an inhibiting response at high doses, resulting in a U- or inverted U-shaped dose response. Toxic agents that are detrimental to human health above certain threshold levels may induce positive effects at a dose that is significantly lower than the NOAEL level. In spite of the evidence for hormesis effects, the topic is still a matter of high controversy among toxicologists. Facing this ambiguity, the article raises the question: how should risk communication be arranged in a situation of high ambiguity, lack of empirical certainty about the effects, major policy dilemmas and significant equity problems? The article summarizes the main results of risk communication research and applies these results to the question of hormesis. First, it explains the main context variables that impact on the success or failure of any risk communication program. These refer to i) the levels of the risk debate, ii) the socio-political style of regulation, iii) different types of audiences, and iv) subcultural prototypes. Secondly, the paper addresses the major functions of risk communication: i) dealing with public perception; ii) gaining trust and credibility; iii) involving stakeholders in the communication process. The last section draws some conclusions for improving risk communication on issues of hormesis.