PURPOSE:This study was designed to assess the clinical manifestations and the risk factors of seizures after hematopoietic stem cell transplantation(HSCT) in children. Also we analyzed the 3-year survival rates of those who experienced such seizures and those who did not. METHOD:The study group consisted of 28 patients(21 males and, 7 females) who experienced seizures out of the 197 patients(113 males and, 84 females) who underwent HSCT at St. Mary's Hospital HSCT Center of the Catholic University of Korea. RESULTS:The overall incidence of seizures developing after HSCT was 13.8%, with boys reporting a higher incidence than girls. No significant difference was found with regards to the onsets and the types of seizures. In terms of the possible risk factors for seizures, the age of the patient and the stage of acute graft versus host disease(aGVHD) were statistically significant. The patients who were 5 years or more showed a 4.2 times greater incidence rate of seizures(P=0.025) than those who were younger. Also, the patients with stage 2-4 aGVHD showed a 2.77 times greater incidence of seizures(P= 0.034) than those with stage 0-1 aGVHD. The 3-year survival rate of the patients experiencing seizures was 37+/-18%, while the rate increased to 67+/-8% for those who did not(P< 0.001). CONCLUSION:Among the recipients of HSCT in children, the patients aged 5 years or older and aGVHD of the stage 2 or above showed a greater likelihood of seizures occurring after HSCT. The patients who experienced seizures should undergo a close observation and an intensive care since those patients reported a lower 3-year survival rate than those who did not.