BACKGROUND: The expression of the adhesion molecules on the cell surface is important in the movement of cells and the modulation of immune response. DILD starts as an alveolitis and progresses to pulmonary fibrosis. So adhesion molecules in these patients is expected to be increased. There are several reports about adhesion molecules in DILD in terms of the percentage of positive cells in immuno-stain, in which the interpretation is subjective and the data were variable. METHODS: So we measured the relative median fluorescence intensity(RMFI) which is the ratio of the FI emitted by bound primary monoclonal antibody to FI emitted by isotypic control antibody of the cells in BALF of 28 patients with DILD(IPF:10, collagen disease:7, sarcoidosis:9, hypersensitivity pneumonitis:2) and 9 healthy control. RESULTS: RMFI of the ICAM-1 on AM(3.30+/-1.16) and lymphocyte(5.39+/-.70) of DILD were increased significantly than normal control(0.93+/-0.18, 1.06+/-0.21, respectively, p=0.001, P=0.003). RMFI of the CD18 on lymphocyte was also higher(24.9+/-14.9) than normal(4.59+/-3.77, p=0.0023). And there was a correlation between RMFI of ICAM on AM and the % of AM(r=-0.66, p=0.0001) and lymphocyte(r=0.447, p=0.0116) in BALF. Also RMFI of ICAM on lymphocyte had a significant (r=0.593, p=0.075) correlation with the % of IL-2R(+) lymphocyte in BALF. The soluble ICAM(sICAM) in serum was also significantly elevated in DILD(499.7 +/-222.2 ng/ml) compred to normal(199.0+/-38.9) (p=0.00097) and sICAM in BAL fluid was also significantly higher than normal control group(41.8+/-23.0 ng/ml vs 20.1 +/-13.6 ng/ml). There was a Significant correlation between sICAM level in serum and the expression of ICAM-1 on AM(r=0.554, p=0.0259). CONCLUSION: These data suggest that in DILD the expression of adhesion molecules is increased in the AM and BAL lymphocytes with elevated serum sICAM, and these parameter may be useful in determining disease activity.