Manufacturers wish to communicate the benefits of probiotics in advertising and labeling with lawful and adequately substantiated claims. Regulatory and substantiation requirements differ for products intended to cure, treat, prevent, or mitigate a disease; to reduce a healthy individual's risk of developing a disease; or to affect the structure or function of the body. Food labeling is regulated by the US Food and Drug Administration, and advertising is regulated by the Federal Trade Commission; the standards and methods used by these agencies differ. Food manufacturers must design their claims regarding the benefits of probiotics with the regulatory environment in mind and must develop their research plans to provide evidence that satisfies the agencies' substantiation requirements. This article offers an overview of the applicable laws and regulations, what they mandate regarding legitimate claims, and the issues regarding the design of research to substantiate such claims.