Bronchoalveolar lavage (BAL) is a well-established diagnostic tool for the assessment of pulmonary diseases in adults. How BAL contributes to the diagnostic process in childhood lung diseases is less clear. One of the problems in interpreting BAL findings in children is that there are few reference data for BAL fluid constituents in children. This report addresses some of the technical problems of bronchoalveolar lavage in children and summarizes current knowledge on cellular and noncellular bronchoalveolar lavage fluid components in children without lung disease.