Consumer product warnings, often placards, buzzers, etc., are information displays that attempt to influence user behavior through the information presented. A review and background of warnings is presented. Assumptions underlying their employment and the lack of scientific validation of their effectiveness are discussed. Quantitative criteria are proposed for the use of warnings based on risk analysis. Examples of such analysis are presented. The limited information processing capability of man dictates that warnings be reserved for significant risks in the context of the products use, environment, and risks from other products. Contraindications for use of warnings are discussed.