After a single oral dose of 0.5 or 0.75 g. of aureomycin in fasting normal subjects, antibiotic activity was recovered in the urine for more than 33 - 55 hrs. The antibiotic was excreted in high concns. between 2 and 16 hrs. and the largest rate of excretion occurred between 2 and 8 hrs. The findings suggest that the opt. intervals between oral doses of aureomycin should be about 8 hrs.