Integrin-immunoglobulin family ligand (CAMs) interactions between lung parenchymal cells (fibroblasts and epithelial cells) and integrin-extracellular matrix component interactions may be involved in the pathogenesis of idiopathic interstitial pneumonia (IIP). Among these, CD34 immunoquantitation allows determination of the degree of vascular proliferation (angiogenesis), whereas VCAM-1 immunoquantitation allows evaluation of the degree of endothelial activity and is strong evidence of inflammation. To validate the importance of vascular proliferation and endothelial cell activity within the alveolar walls and to explore the quantitative relationship between this factor and organizing fibrosis after parenchymal remodeling, we studied surgical lung biopsies in major IIP histologic patterns. We evaluated alveolar vascularity and activity in relation to the various degrees of organizing fibrosis in surgical lung biopsies of diffuse alveolar damage, nonspecific interstitial pneumonia, and usual interstitial pneumonia. Alveolar capillary endothelial cells were intensely immunoreactive with CD34 and VCAM-1. Vascular activity progressively increased in no-organizing fibrotic areas (normal, collapsed, and inflammatory septal areas), whereas vascular density gradually decreased as the degree of organizing fibrosis increased and was lower than that in control lungs in the most extensively fibrotic lesions (mural organizing fibrosis of usual interstitial pneumonia). These results indicate the presence of temporal nonhomogeneic vascular remodeling indiopathic interstitial pneumonia.