The penetration of mercury through the skin of rabbits has been assayed in the case of two mercury ointments which differ only in that one contains resorcinol. The assay consisted in measuring the mercury concentration of the kidneys after twenty-four hours of topical application. The kidneys of rabbits exposed to the resorcinol-containing ointment had an average mercury concentration only one-sixth that of the group exposed to the resorcinol-free ointment. In an assay for bacteriostatic power, using the Food and Drug Administration agar cup-plate method, the resorcinol-containing ointment gave an inhibition zone over twice as wide as that shown by the resorcinol-free ointment.