Objective: Evaluate the efficacy of the ampicillin-quinolone association in the treatment of severe community-acquired pneumonia. Design: Open, prospective study carried out at the Emergency room of the Hospital Universitário da Universidade Federal de Juiz de Fora. Patients and methods: From March 1994 to September 1995, the authors studied 23 patients with fever and with at least three of the following symptoms: cough, purulent sputum, pleuritic thoracic pain, leukocytosis or leukopenia, and a chest radiological examination showing infiltrations compatible with pneumonia diagnosis. The patient diagnosis would be severe pneumonia if he met the criteria of severe sepsis as established by the American College of Chest Physicians and by the Society of Critical Care Medicine. Results: 23 patients were studied. One was excluded after having a pulmonary tuberculosis diagnosis; 21 patients were considered cured and one died. Adverse drug effects occurred in one patient who presented a mild pharmacodermia. Conclusion: Ampicillin-quinolone is efficient in the treatment of severe community-acquired pneumonia.