Dipotassium β-glycyrrhizinate(GK2)is a saponin originated from "Kanzo" plant. We studied such two functions of GK2 as a drug carrier and a penetration enhancer on the eye mucosa. The interactions of GK2 with various drugs were investigated using the 1-octanol/water partition method. GK2 increased the partition of cationic drugs, i.e., antihistamines(chlorpheniramine maleate (CM), diphenhydramine hydrochloride (DH)), as well as decongestants(naphazoline hydrochloride (NA), tetrahydrozoline hydrochloride (TH)). The carrier effect of GK2 is remarkable at its concentration above critical miceller concentration (CMC) and, especially at its pH value of between 4 to 5, resulting that transfers of drugs increased 2 to 10 times as compared to drugs without GK2. In vivo experiments were carried out using rats and rabbits. The effect of GK2 on the inhibition efficiency by CM was evaluated using experimental conjunctivitis formed by injection of histamin on rat upper eyelid. The Inhibition efficiency of edema by CM with GK2 was 4 times stronger than that without GK2. Cornea permeability of TH increased 1.8 times by the addition of GK2. These results indicated that GK2 is applicable as a carrier of cationic drugs on the eye mucosa and cornea.