Augmentin and oxytetracycline were compared in the treatment of chest infections in general practice in an investigator-blind study of 748 patients randomly allocated to 7 days' treatment with standard doses of either Augmentin or oxytetracycline. Significantly more patients treated with Augmentin had a good overall response to therapy both at day 7 (P less than 0.001) and at day 14 (P less than 0.01). The differences between treatments were less marked for individual signs and symptoms of lower respiratory tract infections, due to smaller numbers of patients with any particular symptom. Augmentin, however, was significantly more effective than oxytetracycline in the resolution of chest pain at day 7 (P less than 0.025) and cough at day 14 (P less than 0.005). Sputum purulence was also cleared more effectively by Augmentin by day 14 (P less than 0.001). Both treatments were well tolerated, with no significant difference between treatments in the small number of adverse events. Augmentin has been shown to be an effective, well tolerated treatment for chest infections, superior to oxytetracycline in efficacy and possibly in speed of resolution of clinical symptoms.