Bronchoalveolar lavage (BAL) offers great opportunities in the study of pulmonary diseases. It is safe and noninvasive technique, with similar possibilities than other invasive diagnostic methods and allo-wind repetitions. With the obtained sample, we can assess what happens at the bronchial level as well as the alveolar structures. The introduction of new study methods has increased its profitability in several respiratory pathologies: analysis of tumoral markers in lung cancer, monoclonal antibodies in histiocytosis X, and so on. The BAL can be considered a technique of diagnosis, follow-up, prognosis and evaluation in pulmonary diseases.