SummaryA double blind study comparing the activity of the association of sulfamethoxazoletrimethoprim with the activity of démethylchlortetracycline on 40 cases of acute bronchopulmonary infection is reported. The results demonstrate the superior efficacy of the chemotherapeutic combination, to the antibiotic in the used dosages ; 71 % against 48 % success rate.The necessity of prolonged treatment (10—15 days) with both medications as emphasized. The signs of intolerance of the chemotherapetic SMT are limited to the digestive tract and affect only a small number of patients (11 %). No evidence of systemic toxic effect was noted.