In summary, is well known that at least a 50% of the episodes of AECOPD might be associated with pathogenic bacteria in the lower respiratory tract. Prescription of antibiotics is wide and generalized in hospitalized patients. Clinical trials have shown correlation between AECOPD with sputum purulence (which correlates with presence of bacteria), however they've not included NON-purulent AECOPD, even though they're a significative group of patients hospitalized by this cause too. It's necessary to evaluate the efficacy nor the security of antibiotic treatment in this group of patients in a well designed trial.