To evaluate the bronchial inflammatory response and its relationship to bacterial colonization in bronchiectasis, we performed a bronchoalveolar lavage (BAL) in 49 patients in stable clinical condition and in nine control subjects. BAL was processed for differential cell count, quantitative bacteriologic cultures, and measurement of inflammatory mediators. An increase was observed in the percentage of neutrophils (37 [0 to 98]) (median[range]) versus 1[0 to 4]%, p = 0.01), in the concentration of elastase (90.5 [8 to 2,930] versus 34 [9 to 44], p = 0.03), myeloperoxidase (9.1 [0 to 376] versus 0.3 [0.1 to 1.4], p = 0.01), and in the levels of TNF-alpha (4 [0 to 186] versus 0 [0 to 7], p = 0.03), IL-8 (195 [0 to 5,520] versus 3 [0 to 31], p = 0.001), and IL-6 (6 [0 to 115] versus 0 [0 to 3], p = 0.001) in patients with bronchiectasis compared with control subjects. Noncolonized patients showed a more intense bronchial inflammatory reaction than did control subjects. This inflammatory reaction was exaggerated in patients colonized by microorganisms with potential pathogenicity (MPP), with a clear relationship with the bronchial bacterial load. Patients with bronchiectasis showed a slight systemic inflammatory response, with poor correlations between systemic and bronchial inflammatory mediators, suggesting that the inflammatory process was mostly compartmentalized. We conclude that patients with bronchiectasis in a stable clinical condition present an active neutrophilic inflammation in the airways that is exaggerated by the presence of MPP, and the higher the bacterial load the more intense the inflammation.