The Chilean Society of Respiratory Diseases (SER) developed guidelines for the empirical treatment of community acquired pneumonia (CAP). Aim: To evaluate the degree of adherence to antibiotic treatment recommended by SER guidelines and its influence on medical outcomes. Patients and Methods: We prospectively evaluated 453 consecutive immunocompetent adults (mean age±SD: 69±19 years) hospitalized for CAP. Patients were stratified according to the Pneumonia Severity Index (PSI), and initial antibiotic regimen was classified as being consistent or inconsistent with the SER guidelines. Rate of medical complications, switch therapy rate, length of stay (LOS), and 30 days mortality were compared between those treated consistently or inconsistently with the SER guidelines. Results: Adherence to SER guidelines was 46%. Patients treated consistently with the SER guidelines were older (mean age±SD: 72±16 v/s 65±20 years), had more comorbidities (84 v/s 69%) and a higher proportion belonged to the high-risk PSI categories (69 v/s 49%). There were no significant differences in medical complication rate, switch therapy rate or LOS between both groups. Adherence to SER guidelines did not affect mortality after adjusting for PSI and for prognostic factors associated with 30 days mortality by multivariate analysis. Conclusions: The degree of adherence to antibiotic treatment recommended by SER guidelines was moderate and they were applied mainly in patients with high risk CAP. This fact can explain the lack of evidence of improved medical outcome in patients treated according to SER guidelines (Rev Méd Chile 2003; 131: 847-56)