Based on the results of a study on pulmonary tissue uptake of flomoxef (FMOX), a new antibiotic agent, in 45 patients undergoing thoracotomy, the following conclusions were drawn: 1. Immediately preoperative 1 hour-drug infusion of 1 g FMOX led to maximum serum concentration (averaging 42.4 micrograms/ml) 1 hour later, with a half-life of its beta phase of 1.26 hours. 2. Normal lung (alveolar) tissue concentration was Cmax 17.98 micrograms/g with its ratios to serum peak value being 31.8, 27.1, 22.2, 9.4, 5.9 and 5.0% at 1, 2, 3, 4, 5 and 6 hours later, respectively. 3. Bronchiolar tissue concentration was Cmax 31.91 micrograms/g, with its ratios to serum peak value being 27.8, 19.3 and 10.1% at 2, 3 and 4 hours later, respectively, indicating its good bronchiolar intra-tissue transition. The above results suggested the usefulness of FMOX for both the treatment of respiratory infections and the prevention of postoperative infections.