Bronchoalveolar lavage (BAL) is a bronchoscopic technique that reveals specific insight in the distal parts of lung parenchyma. During the past twenty years, research of cellular and extracellular bronchoalveolar profiles gave important information on pathogenesis of some pulmonary disorders, promoting this technique as a diagnostic tool in pulmonary infections and interstitial lung diseases. Bronchoalveolar lavage is a safe, well-tolerated and suitable diagnostic procedure in immunocompromised patients. The patients with alveolar proteinosis gain therapeutic benefit of bronchoalveolar lavage. In this article we described technical notes, sampling, storage, cellular and noncellular analyses of bronchoalveolar lavage, including interpretation of results and significance in pulmonary diseases.