Cefuroxime axetil was compared with cefaclor for the therapy for lower respiratory tract infections. Sixty-one patients were randomized to receive the following drug dosages: (1) cefuroxime axetil, 250 mg orally every 12 hours (21 patients); (2) cefuroxime axetil, 500 mg orally every 12 hours (21 patients); and (3) cefaclor, 500 mg orally every eight hours (19 patients). Of these 61 patients, 80% were male, with a mean age of 59.5 years; 56% had acute pneumonia, and the remainder had an acute bronchitis. Causative pathogens included typical respiratory tract pathogens. Overall, 23 of 27 patients with bronchitis were clinically cured at the end of therapy. Thirty-one of 34 pneumonias were clinically cured or improved at the end of therapy; the three pneumonia treatment failures occurred in the lower dose cefuroxime (n = 2) and cefaclor (n = 1) treatment groups. Overall, bacteriologic cure occurred in 86% of patients treated with 500 mg of cefuroxime axetil compared with 60% of cefaclor-treated patients. Adverse clinical effects were uncommon. From this study, it was concluded that cefuroxime given every 12 hours is at least as clinically efficacious as cefaclor; it is a new oral cephalosporin with pharmacologic and bacterial spectrum advantages over many older agents.