Abstract: Aim In this study, 58 paediatric patients were prospectively evaluated with a number of screening studies performed between 0 and 180 days after allogenic hematopoietic stem cells transplantation (HSTC) to detect any risk factors for developing oral manifestations of acute Graft-versus-Host Disease (a-GvHD). Materials and methods A total of 58 paediatric allogenic HSTC patients (37 males aged 1 to 15, and 21 females aged 4 to 18), entered the study and were observed by a trained dental team for a period of 6 months following transplantation while assuming cyclosporine, an immunosuppressive agent with a-GvHD prophylactic activity. Mean age at transplantation was 7.2 years old. Screening studies included physical examination, complete blood counts and liver function tests. Complete extraoral and intraoral clinical examinations were performed for all patients to detect oral lesions. Furthermore, some variables (sex, number of HSTC performed in the same patient, degree of HLA disparity and the positive/negative result of cytomegalovirus antigenemia test during the three months after engraftment) were investigated in the attempt to evaluate their predictive and/or diagnostic value in paediatric HSTC recipients. The resulting data were analysed with the Fisher's exact test. Results Twenty-two percent of the patients developed oral manifestations of a-GvHD. Oral symptoms frequently are the major complaints of the patients during the follow-up period. The oral changes included mucositis, erosions and/or ulcerations; xerostomia, pain and bleeding were also referred. The variables investigated for predictive and/or diagnostic value in paediatric HSTC recipients included: sex (relative risk 0.494, 95% confidence interval 0.119-2.052, P= 0.1242); number of HSTC performed in the same patient (relative risk 5.4, 95% confidence interval 0759-3.843; P= 0.0714); degree of HLA disparity (relative risk 0.24, 95% confidence interval 0.058-0987, P= 0.0428); and the result to cytomegalovirus (CMV) antigenemia test during the three months after engraftment (relative risk 0.86, 95% confidence interval 0.273-2.712, P= 1). Conclusion Patients presenting two or more risk factors should be closely monitored for development of clinical oral a-GVHD, as oral complications are a significant cause of morbidity and potential mortality for children undergoing HSTC and can interfere significantly with transplant recovery.