Scientific controversies are associated with significant uncertainty. Despite this uncertainty, available knowledge must be communicated to the public, who are potentially at risk. There are contradictions in the existing literature about the value of communicating uncertainty associated with science. Some scientists and decision-makers believe that communicating uncertainty to the public will produce panic and confusion, and will discredit science. Others believe that uncertainty must be communicated to increase trust in science. We tested reactions to communication about uncertainty related to the controversial link between exposure to endocrine disrupters and a decline in human male fertility. Our empirical setup used focus groups and qualitative analysis of participants' perceived uncertainty and their emotions. The results show that laypeople raise more and different uncertainties than those communicated by researchers. Moreover, laypeople did not react to uncertainty globally;' they had different reactions to the different sources of uncertainty. Uncertainty did not elicit panic in this case study. Rather, uncertainty was reassuring, except when it was associated with an inability to precisely identify and, therefore, control the cause of male reproductive disorders. We discuss the emotions expressed and their relationships with communication about scientific uncertainty (powerlessness, guilt, outrage, etc.). We also note that feelings of confusion increase after uncertainty has been communicated.