William R. Warner & Co. v. Eli Lilly & Co.

Eli Lilly (plaintiff) sold a chocolate-and-quinine remedy under the mark Coco-Quinine; William R. Warner & Co. (defendant) later sold a nearly identical product as Quin-Coco. Warner's salespeople induced retailers to fill Coco-Quinine orders with the cheaper Quin-Coco. Eli Lilly sued for trademark infringement and unfair competition. The district court denied relief; the court of appeals rejected the trademark claim but found unfair competition, and Warner appealed.

Whether a seller commits unfair competition by inducing retailers to substitute and pass off its own product as that of a competitor, even where the competitor's mark is descriptive and its formula may be lawfully copied.