A clinical sudy of ofloxacin, a new synthetic antibacterial agent, for 24 patients with acute oral and maxillofacial infections was undertaken. Ofloxacin was orally given at a dose of 200mg three times a day to all patients. The results were as follows:1. The clinical response rate was 87.5%. Side effects were not observed in any patient. The elevation of S-GOT, and S-GPT was observed after ofloxacin administration in one case in the laboratory examinations.2.In vitro, ofloxacin showed high antibacterial activity mainly against α-streptococcus, isolated from suppurative lesions.These rsults suggested that ofloxacin is a useful antibacterial agent against oral and maxillofacial infection.