IN THE past year several reports have been made concerning the stability of penicillin in solution or in ointment mixture. Gots and Glazer 1 found that specimens of solution and ointment containing 1,000 units per cubic centimeter remain active for approximately one month at room temperature. Kirby 2 found "considerable activity" in an istonic solution of sodium chloride containing 100 units per cubic centimeter after remaining in an open bottle for five months. Stein, 3 using 19,285 units per gram, reported that his ointment retained about 80 per cent of its original strength after five weeks at room temperature in the tropics. On the other hand Milner 4 claimed that penicillin retained its potency for only four hours when in solution (500 units per cubic centimeter) and for six hours when in ointment form (100 units per gram). Sugar, 5 using 2,500 units per gram in a water-soluble jelly base,