The present study aimed at investigating the possible effect of human cordblood mesenchymal stem cell (SC) therapy on fibrosing interstitial pulmonary disease. This was accomplished by using amiodarone (AM) as a model of inducedlung damage in albino rat. Thirty adult male albino rats were divided into 3 groups: Group1 (Control group) of 5 rats. Group 2 (Amiodarone group) of 15 rats each receiving 30mg/kg of AM. Lung damage was confirmed 6 weeks later. The animals of group 2 were subdivided into subgroups 2A, 2B and 2C, each of 5 animals sacrificed 6, 8 and 10 weeks following confirmation of lung damage respectively. Group 3 (Stem cell therapy group) of 10 rats injected with cultured stem cells (SCs) 8 and 10 weeks following confirmation of lung damage. Cord blood collection, SCs isolation, culture and labeling were performed. Lung specimens were subjected to histological (H&E and Masson's trichrome stain), histochemical (Prussian blue stain), immunohistochemical (CD105), morphometric and statistical studies. In subgroup 2A, few bronchioles with partially obliterated lumen were surrounded by dense infiltration. Thickened interalveolar septa with congested, distended venules and mononuclear infiltrating cells including fibroblasts were seen. Some arterioles appeared congested with thickening of their wall.. The alveoli were lined by few cells containing flat nuclei. Congested capillaries were noticed in the interalveolar septa and shed cells were seen in some alveolar spaces. In subgroup 2B, occasional large bronchioles with shed epithelial cells, RBCs in the lumen and infiltrating cells in the adventitia were observed. Obviously thickened interalveolar septa with few patent alveoli were evident. These septa contained pulmonary arterioles and congested venules with obviously thickened walls. Few patent alveoli surrounded by dense mononuclear infiltrating cells, including fibroblasts appeared. No obvious lining alveolar epithelium was evident. Instead, plasma cells and few mononuclear cells were observed in the alveoli. Subgroup 2C showed some small bronchioles with partial obliteration of the lumen, marked thickening of the wall of some arterioles and thickened wall of some smaller arterioles. Markedly thickened interalveolar septa with collapsed alveoli and cellular debris were found in the lumen of few alveoli. Multiple fibroblasts and fibrocytes existed in the interalveolar septa and in the lumen of the alveoli. No lining alveolar epithelium was detected. Stem cell therapy group revealed Prussian blue and CD 105 positive cells of variable shapes near blood vessels, in the interalveolar septa, at the bronchiolar epithelium and in the adventitia of the bronchioles. The mean area of collagen fibres denoted a significant increase in AM subgroups compared to control and SC therapy groups.Cord blood mesenchymal SC therapy proved definite amelioration of lung fibrosis, airway obstruction and pulmonary hypertension provided therapy starts early in the development of the pathogenesis.