I have been interested in the potential use of penicillin as a dermatologic bacterial inhibitor for the last twelve months.1 Recently I have used penicillin purified in a water-miscible oxycholesterol-petrolatum base2 with such success that I believe a note on its use and preparation is warranted. Twenty-five cases, including cases of impetigo contagiosa, infectious eczematoid dermatitis, dermatitis repens, furunculosis, interdigital pyoderma of the feet, lymphangitis (localized), sycosis vulgaris and acne necrotica, were studied. The impetiginous crusts were left intact, and débridement was done to the pyodermic lesions three to five days after the initial visit. For several months I have been collecting "empty" penicillin bottles used at Queens hospital. They had contained 100,000 units of penicillin per bottle, which had been diluted with sterile isotonic solution of sodium chloride to give 10,000 units per cubic centimeter. The "empty" bottles previously were thrown away by