AUREOMYCIN, isolated by Duggar in 1948,1is an antibiotic biosynthesized by the actinomycete, Streptomyces aureofaciens. It has attained great clinical significance because of its therapeutic activity against a wide bacterial spectrum, which includes a number of Gram-positive and Gram-negative organisms, and it appears to be highly specific against many members of the rickettsial group and some virus-like agents. The antibiotic is a yellow powder said to be soluble in distilled water and in 5% dextrose solution in distilled water. Solutions in isotonic sodium chloride solution precipitate when a level of more than 1% of the drug is attained. The aqueous solutions are acid and when neutralized or made alkaline deterioration of activity is rapid at room temperature. After oral administration of a single dose of 0.5 gm., aureomycin appears in the urine in 1 hour and is detectable up to 16 hours, the peak concentration occurring between 2 and