The results of an open randomised trial comparing the efficacy of parenteral and oral ofloxacin with that of amoxycillin clavulanate are reported. Of 121 patients enrolled, 92 were clinically evaluable, of whom 59 were treated with ofloxacin and 33 with amoxycillin clavulanate. In the ofloxacin group all patients improved clinically, while in the amoxycillin clavulanate group 94% improved and 6% were clinical failures. In the ofloxacin group 95% showed satisfactory bacteriological response, while in the amoxicillin clavulanate group the bacteriological response was judged satisfactory in 82% of the patients. Seven percent of the patients had mild side effects (headache, nausea, vomiting and skin rashes). All of these side effects disappeared after treatment. We conclude that ofloxacin is a safe and effective drug in oral and parenteral forms for the treatment of lower respiratory tract infections.