To evaluate which factors are associated with alterations in pubertal development in pediatric patients with leukemia in the surveillance phase.A case-control study was carried out, including patients aged 8-14 years with diagnosis of acute lymphoblastic leukemia under surveillance. Demographic data were collected, age at diagnosis, type of leukemia, risk of leukemia, duration and type of treatment received, time of surveillance phase; and pubertal development was assessed by Tanner stage, bone age, pelvic ultrasound for women, and LH levels. Fisher's exact test and Mann-Whitney U-test were used.Twenty-five pediatric patients with a diagnosis of acute lymphoblastic leukemia between 8 and 14 years of age with a median of 8 were included, only 4 (16%) presented pubertal alterations, 1 had pubertal delay and 3 advanced puberty. The history of radiotherapy was related to pubertal alterations (p = 0.03).The antecedent of having received radiotherapy as part of the treatment in patients with acute lymphoblastic leukemia is a risk factor for developing pubertal abnormalities.Copyright: © 2017 SecretarÍa de Salud