Myeloablative chemotherapy used prior stem cell transplantation produces epithelial injury including oral cavity. Both damage by chemotherapy and subsequent infections cause mucositis. The aim of the study was to evaluate mucositis in a group of 31 patients. Patients aged 18-67 yrs (mean 42 yrs): 28 with blood neoplasms and 3 with aplastic anemia, were observed on days 0, 3, 5, 7, 9, 14 and 30 after transplantation of haematopoietic cells (autologous in 20 cases and allogeneic in 11 cases). The intensity of mucosal inflammation was evaluated according to 3 scales: WHO, Bearmann and 5-degree scale developed by the authors. This last scale, unlike other scales, was based on an accurate stomatological evaluation of the mucosal changes. A positive correlation was found between the intensity of mucosal inflammation and granulocytopenia <500/microl (p<0.01) and also between the presence of petechiae with blood platelet level <20.000/microl (p<0.001).