ALTHOUGH the infectious etiology of acute nonspecific primary lung abscess has not been established, it has been the general experience that most of the cases respond to penicillin G. The treatment in wide usage requires frequent injections for many weeks. The optimal regimen with regard to dosage, route of administration, and duration of therapy has not been determined. Since the parenteral method is inconvenient to nursing personnel and annoying to patients, orally administered penicillin is worth consideration. The present study was undertaken to investigate the efficacy of treating acute nonspecific primary pulmonary suppuration with large doses of penicillin G by mouth. In the past, the authors have treated acute lung abscess successfully with aqueous penicillin G in a dosage of 300,000 units intramuscularly every six hours. On the basis of pharmacologic studies1 an oral dosage of four times the intramuscular amount was considered likely to be effective. The regimen used