Ceftibuten is an oral third generation cephalosporin with potent antimicrobial activity against Enterobacteriaceae, beta-lactamase positive Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis, Neisseria gonorrheae, penicillin-susceptible pneumococci, and beta-hemolytic streptococci. To study the efficacy and safety of ceftibuten for treatment of bronchitis, 58 patients were randomized to therapy with either ceftibuten 400 mg once a day or cefaclor 250 mg every 8 h at a ratio of two to one. Of 45 clinically evaluable patients, 28 (87.5%) of the 32 ceftibuten patients and 12 (92.3%) of the 13 cefaclor patients were clinically improved or cured. Of 33 microbiologically evaluable patients, 21 (87.5%) of the 24 ceftibuten patients and eight (80%) of the ten cefaclor patients were cured. Of 56 patients evaluable for adverse effects, three (7.9%) of the 38 ceftibuten patients and one (5.6%) of the 18 cefaclor patients had adverse reactions. In this small study, once-daily ceftibuten appeared as safe and as effective as cefaclor for the treatment of bronchitis.