The Brazilian Cooperative Group for Treatment of Childhood Acute Lymphocytic Leukemia (GBTLI) has started clinical activities trials in 1980. Three consecutive multicenter studies in children with unprevious treated ALL have been completed including 994 patients. The first GBTLI-80 accrued 203 children from 1980 to 1982. It was delineated with the standard three drugs induction therapy, CNS protection for all pts comprised cranial irradiation and intrathecal Methotrexate. For low risk pts cranial irradiation with 18Gy was compared in a randomized trial with 24Gy. Maintenance therapy continued for 120 weeks. The 12 years of the event free survival rates for all risk groups is 50% (SD 5%). Regarding CNS relapses there was no significant statistical difference between pts that received 18 or 24Gy. The treatment strategy of GBTLI-82 (n = 360) from 1982 to 1985, consisted of the same previous induction, consolidation, CNS therapy with cranial irradiation 18 Gy (low risk) or 24Gy (high risk), followed by continuous maintenance for 2 years. The main question in this study was the comparison between sequential rotation or pulses of 3 pairs of drugs during maintenance. At a median follow-up of 10 years, the overall event free survival rates for all children is 58% (SD 4%). There was no significant difference between the two maintenance regimens. The successor GBTLI-85 ran from 1985 to 1988 and registered 431 pts. For the first time no cranial radiation was given to children with very good prognosis. For them, CNS protection was done with triple intrathecal therapy during all treatment. A consolidation therapy with high dose ARA-C was introduced for high risk pts and infants The 6.5 years event free survival for all children is 70% (SD 4%). Significant better results were achieved for high risk and infants pts (EFS 50%). Early intensification therapy and rotational combination chemotherapy improved the outcome in childhood ALL in Brazil.