Based on its potential role in adult myelodysplastic syndrome (MDS), the Children's Oncology Group (COG) embarked on a phase II study using amifostine in pediatric MDS (WHO 2001 criteria) patients. Responses were evaluated after two cycles. Ten patients were enrolled; five were deemed ineligible, and four withdrew after the first course. Only one patient completed two courses, and was found to be in complete remission. The study was closed after being open for 2 years due to slow accrual. Studying a rare disease like MDS may pose insurmountable obstacles even in a large clinical trials group such as COG, in part because of the changing definitions of MDS and the rarity of adult type MDS in children. The role of amifostine in pediatric MDS was not known at the time of study. Pediatr Blood Cancer 2011 Wiley-Liss, Inc.