Abstract6‐Phenyl‐2‐pyrone‐3‐carboxylic acid has been prepared by acid hydrolysis of its ethyl ester and by the action of sulfuric acid on its isomer, 2‐carboxy‐5‐phenyl‐2‐penten‐4‐yn‐1‐oic acid. The distinction between these two isomers and a third, 2‐carboxy‐5‐phenyl‐2,4‐pentadien‐(1,4)olide, is set forth. A fourth isomer, 3‐phenyl‐2‐pyrone‐6‐carboxylic acid, has been synthesized by acid hydrolysis and