Lung surfactant protein A (SP-A) and Clara cell 10-kDa protein (CC10) are the most abundant proteins produced locally in the lower respiratory tract, as assessed in bronchoalveolar lavage (BAL) analysis. However, it is not known what factors influence SP-A and CC10 levels in BAL fluids, and the relationship between SP-A and CC10 levels in BAL fluids has been unclear. We measured SP-A and CC10 concentrations in BAL fluids from 11 healthy nonsmokers and 12 healthy smokers by enzyme-linked immunosorbent assays using specific antibodies. Mean SP-A and CC10 levels in BAL fluids of healthy smokers were significantly lower than those of healthy nonsmokers. SP-A values correlated significantly with CC10 and phospholipid values in BAL fluids. On BAL examinations using three 50-ml aliquots, the mean SP-A level in the second lavage was 2.0-fold and 2.4-fold, respectively, of that in the first and third lavages, and the mean CC10 level in the first lavage was 5.0-fold and 5.6-fold, respectively, of that in the second and third lavages. We conclude that BAL fluid SP-A and CC10 levels are influenced by the BAL methods and by cigarette smoking. There is a significant positive correlation between SP-A and CC10 values in BAL fluids of healthy subjects.