Cefixime (CFIX) was administered 200 mg (2 divided doses) per day to 154 female patients with acute uncomplicated cystitis. Ninety four of the 154 patients who satisfied the criteria proposed by the UTI Committee, Japan were examined for the efficacy of the treatment, but 151 of 154 patients were included in the study of the side effects of the drug. The overall clinical efficacy was excellent in 80.8% and moderate in 18.1% of the patients. Ninety five (97.9%) of 97 strains which were isolated from the patients were eradicated in the urinary specimens by the treatment. Subjective side effects were observed in only one (0.7%) of the 151 patients, who complained of a sensation of heaviness in the head. No drug-related aggravation in the laboratory test was observed except for three patients who showed mild elevation glutamic pyruvic transaminase, alkaline phosphatase and blood urea nitrogen. These results showed that the oral administration of CFIX was excellent and satisfactory in the treatment for acute uncomplicated cystitis.