In order to evaluate the puberal development of girls treated by Acute Lymphocytic Leukaemia (ALL) a retrospective study was done at Campinas-SP, Brazil. Forty two girls were treated by ALL with either 18 or 24 Grays of cranial irradiation. All patients were treated with chemotherapy including intrathecal methotrexate in similar dose regimens in either groups. The results showed lower mean ages at telarche, pubarche and menarche in the treated group, mainly in the group treated before five years old. No differences were observed in the 18 Grays or 24 Grays group. Our data suggest that girls treated by ALL have a precocious puberal development.44214-7