Abstract: In the experiment Valia-Chien skin permeation cell and methods were constructed for investigating the influence of various vehicles on the transdermal absorption of norgestrel (NG)and levonorgestrel (LNG). All of the vehicles were saturated with NG or LNG at 37℃, so variations in permeation were mainly attributable to the vehicle effects. The results showed that the transdermal fluxes of NG and LNG were increased about 5～6 fold using an optimal concentration range of aqueous ethanol as a vehicle relative to that when normal saline was used as a vehicle. The NG permeation rate was about 1～2 fold greater than that of LNG in the above-mentioned saline, aqueous ethanol and neat ethanol. Oleic acid (OA) and aqueous ethanol both enhanced synergistically the permeation of LNG through the human cadaver skin. When OA--80% ethanol(0.75 : 9.25ⅴ/ⅴ)was used as a co- vehicle, the flux of LNG was 0.53μg/cm²· h, which was 3 fold and 29 fold respectively greater than that when 80% ethanol and neat OA were used as the vehicle.