We report the case of a 14-year-old male treated with arsenic trioxide for recurrent acute promyelocytic leukemia. He developed hyperleukocytosis (WBC 111.6 × 109/L) which then resolved while continuing daily arsenic. Hyperleukocytosis without other complications may not be an indication for adding cytotoxic therapy or steroids, nor for discontinuing arsenic trioxide therapy in children. Pediatr Blood Cancer 2008;50:1265–1267. © 2008 Wiley-Liss, Inc.