RUNX1 over-representation is present in children with acute lymphoblastic leukemia. Although these cases have been related with poor outcome, not all reports describe patient follow-up. To understand its associated clinical features and prognosis, we report on 14 children with ALL and RUNX1 over-representation with laboratory data and outcomes compared to previous reports. Eighty-six children with RUNX1 over-representation have been described, including the 14 patients of this study. Most of them are between 6 and 15 years of age, have low leukocyte counts, pre-B immunophenotype, and three to eight RUNX1 copies. Of the 69 patients with follow-up data, 21 of them relapsed or died, suggesting that RUNX1 over-representation is associated to a poor outcome.