A new method for quantitative determination of p-methoxycinnamic acid in Scrophulariae radix by high performance liquid chromatography was established. A reversed-phase system with SPHERI-5 RP-18 5 micron $(250;{ imes};4.6;mm)$ column using TFA (0.05%) and acetonitrile as a mobile phase was developed. p-Methoxycinnamic acid and N-(p-methoxycinnamoyl)-p-aminophenol as an internal reference were detected at 310 nm and the analysis was successfully carried out within 50 min.