A method was developed for identifying some of the common phenolic carboxylic acids occurring in natural products. Two chromatographic columns, consisting of the liquid phases silicone gum rubber (SE-30) and diethylene glycol succinate (DEGS), gave well-defined peaks for o-coumaric, p-coumaric, ferulic, m-hydroxybenzoic, p-hydroxybenzoic, protocatechuic, syringic, and vanillic acids.