Erythromycin is commonly used for the empirical treatment of community-acquired pneumonia, but there is some concern about its usefulness when Q fever is suspected because of in-vitro studies showing a lack of efficacy against Coxiella burnetii. This study was undertaken to assess the clinical value of the antibiotic in this setting. Nineteen patients with Q fever pneumonia treated with a variety of antibiotics considered ineffective against C. burnetii, were reviewed. Eleven patients who received erythromycin had a rapid clinical improvement and each became afebrile by the fourth day of treatment. However, only two of eight patients who received other antibiotics improved (both of them had been treated with beta-lactams). Both groups were comparable regarding to age and previous duration and severity of disease. Those patients who did not respond to other antibiotics improved promptly after erythromycin was started. This study suggests that erythromycin is an adequate treatment for Q fever pneumonia.