Abstract: In the present studies, two chamber cells were used to measure antivirotic Ara-ADA permeability through 4～6 weeks-old hairless mouse abdominal skin pretreated with Azone for 24 hours. Continuous effect of enhanced percutaneous penetration with Azone pretreatment was studied. After skirt was pretreated with Azone, permeability coefficients were determined immediatly and after 4,5,6,7,8 days. The results showed that increase of Permeability coefficient reached 44 times after Azone pretreatment. The enhancement can maintain for at least 8 days and lags of diffusion time were distinctly shortened.