Patients with and without interstitial lung disease (ILD) underwent bronchoalveolar lavage (BAL) with 4 boluses of 60 ml of normal saline. Fluid was withdrawn after each bolus, and the results after the first and second bolus were pooled and compared with the results after the third and fourth bolus. In the control group (n = 9), there was a significantly higher percentage of lymphocytes and neutrophils after the first half than after the second half (first half: lymphocytes, 8 +/- 1.9%, mean +/- SEM; neutrophils, 2 +/- 1.2%. Second half: lymphocytes, 5 +/- 1.2% (p less than 0.01); neutrophils, 0.3 +/- 0.12% (p less than 0.05). In the ILD group (n = 8), there was a rise in the number of lymphocytes from 15 +/- 4.9% to 20 +/- 3.9% (p less than 0.05) and the number of neutrophils from 8 +/- 4.8% to 10 +/- 5.6%. The ILD group had more cells aspirated after the second half than after the first half of the BAL, whereas the control group did not. Abnormalities in the cell population of the BAL fluid were more striking when the larger volume was used.