BAL is increasingly used in the assessment of pulmonary diseases, however, the role in children remains to be defined. Therefore bronchoalveolar lavage (BAL) was performed on 21 healthy children in order to enable quantification and characterization of the alveolar cell populations. Reference values for cellular constituents of BAL fluid using rigid bronchoscopes are lacking-even though in children still 90% of bronchoscopies are done by rigid instruments and BAL is performed using a catheter leading into the lower lobe. The children, 12 months to 14 years of age, were lavaged adjusted to body weight with three 1 ml/kg aliquots of normal saline. Recovery was 31 +/- 12%. Each aliquot was analysed separately. The number of total cell count per milliliter was 29.8 x 10(4) (range 0.6-161 x 10(4). Percentages of different cell types of the third simple were (mean): macrophages 88.5, lymphocytes 6.4, neutrophils 4.8, eosinophils 0.1, basophils 0%. Significantly more neutrophils and less lymphocytes were found in the first as compared to the second and third sample. No age dependency was observed for either cell type. The comparison to cellularity of BAL-fluid with proven evidence of Adenovirus, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae type B showed a marked influence of viral and bacterial germs. The study provides the first reference data on BAL differential cytology in healthy children using rigid bronchoscopy.