The most effective treatment of hematologic malignancies and some benign hematological diseases is allogeneic stem cell transplantation therapy. Pulmonary complications can occur after allogeneic stem cell transplantation. And these complications effect mortality and morbidity in these patients. In this study we want to investigate the use of exhaled breath condensate (EBC) collection which is a simple and completely noninvasive method. By this way we hope to detect pulmonary complications early. EBC, has been implicated in the pathophysiology of inflammatory airway diseases such as cystic fibrosis, asthma, chronic obstructive pulmonary disease (COPD) and bronchiectasis. EBC, has not been investigated before in patients who underwent stem cell transplantation.