The aim of the present research was to study the transdermal absorbability of ferulic acid and imperatorin in Zhitong cataplasm. Using methanol to extract the effective components, HPLC was established to determine drug content in Zhitong cataplasm. The excised abdominal skin of nude rats was used as the permeation model Utilizing the modified Franz diffusion cell, the suitable receiving solution was elected. The contents of ferulic acid and imperatorin in Zhitong cataplasm were 455.10, 371.66 microg x g(-1), respectively. Taken 20% ethanol- PBS (pH 8) as receiving solution, ferulic acid and imperatorin could be detected maximize, with the steady-state infiltration rates of 1.29, 0.15 microg x h(-1) x cm(-2), respectively. After 24 h, their penetration quantities were 30.03, 3.31 microg x cm(-2), with the penetration rates of 41.45%, 5.60%, respectively. The residual quantities of ferulic acid and imperatorin in skin were 0.69, 2.60 microg x cm(-2), with the retention rates of 0.95%, 4.40%, respectively. The in vitro transdermal behavior of ferulic acid in Zhitong cataplasm was close to a zero-order process, with the stratum corneum playing a rate-limiting role; whereas the percutaneous behavior of imperatorin was closer to Higuchi model, where diffusion played an important role in drugs permeation.