Governmental health agencies frequently issue warnings about new health hazards (e.g., smoking and excessive drinking). This chapter discusses factors affecting adherence to governmental warnings against the use of household products previously perceived safe. To be effective, a health warning must reach its intended audience and bring about behavior modifi cation. This is challenging because, in order to modify behavior, the warning message must counteract and overpower the effect of habitual safe experience. Indeed the questions of how people perceive such warnings, whether they adhere to them, and what promotes or prevents adherence are central in marketing practice and research.In this chapter, we review the psychological decision-making literature on trust of the source issuing the warning and safe experience with the risk-causing agent. Next we touch on basic requirements of awareness and understanding of the message. We then review the marketing literature on message design, focusing on factors practical for widespread implementation (i.e., vividness of message, one-sided vs. two-sided messages, regulatory fi t). Next, based on behavioral decision research, we discuss how to counteract cognitive and emotional consumer biases that may reduce adherence. Finally, as a case in point, we evaluate adherence to the 2008 United States Food and Drug Administration (FDA) warning against administration of over-thecounter cough and cold medication (OTC-CCM) in children under age 2. We describe the results of three studies that examine whether parents had heard about OTC-CCM warnings and whether they intended to adhere to them. We conclude with recommendations for optimizing the design and dissemination of similar warnings.