Angiogenesis has been implicated in the pathogenesis of interstitial lung diseases. A correlation between serum angiogenic cytokines level of patients with idiopathic pulmonary fibrosis and radiographic manifestations or functional pulmonary changes has been described, but the role of angiogenesis in the pathogenesis of other interstitial lung diseases such as silicosis and pulmonary Langerhans cell histiocytosis remains unclear. The aim of the study was to examine the effect of sera from silicosis and pulmonary Langerhans cell histiocytosis patients on angiogenesis induced by human mononuclear cells (MNC) in relation to pulmonary function. The study population consisted of 12 patients with silicosis, 12 patients with pulmonary Langerhans cell histiocytosis (PLH), and 14 healthy volunteers. Spirometry, whole-body plethysmography, static lung compliance (Cst), and diffusing capacity of the lung for CO (DL(CO)) were performed in all patients. As an angiogenic test, leukocyte induced angiogenesis assay according to Sidky and Auerbach was used. Sera from PLH patients exerted a significant inhibitory effect on angiogenesis (P<0.001). Sera from silicosis patients significantly (P<0.001) stimulated angiogenesis compared with sera from healthy donors. However, sera from healthy donors significantly stimulated the angiogenic activity of MNC compared with the control with PBS. The mean value of DL(CO) was significantly lower in the group of patients with PLH compared with patients with silicosis (P<0.05). A significant correlation between angiogenesis index and DL(CO) was observed (P<0.05). No significant correlation between the angiogenesis index and other functional parameters was found. Sera from interstitial lung diseases patients and healthy donors constitute a source of mediators modulating angiogenesis. Sera from silicosis patients stimulate neovascularization but sera from PLH patients exert an inhibitory effect on angiogenesis. A correlation between serum angiogenic activity and DL(CO) was found.