Dyclonine hydrochloride, a local anesthetic, is known to degrade in aqueous media. In this paper, the isolation and characterization of two major degradation products, formed by heating of an aqueous solution of dyclonine hydrochloride for 2 weeks at 50 degrees C, are presented. The proton and carbon-13 nuclear magnetic resonance, infrared, and mass spectral data reported conclusively show the two products to be 1-(4-butoxyphenyl)-2-propen-1-one and 1-(4-butoxyphenyl)-3-hydroxy-1-propanone. The proton and carbon-13 nuclear magnetic resonance spectral data of the free dyclonine base are also included.