The present paper reports on the penetration of salicylic acid, a substance with high permeability, through swine skin. Liquid scintillation counter and autoradiographic measurements were performed, on the excised swine skin to which ointment had been applied. The results indicated that the substance penetrated mainly through transfollicular route and was deposited transiently at various levels of each follicle, resulting in zig-zag pattern on the liquid scintillation counter curve. The autoradiographic study also revealed a heavy transfollicular pattern of the substance though a slight transepidermal pattern was also noted. Whether the substance penetrates because of its lipid solubility or because of its affinity to the keratinous tissue is still open to question.