Successful treatment of relapsed acute lymphoblastic leukemia (ALL) is one of the biggest challenges in pediatric hematooncology at the beginning of the 21st century. The authors analyze a group of 85 children suffering first relapse of ALL in the Czech Republic between 1990–2000. The probability of 4-year event-free survival (EFS) was 16.7% (SE 5%) and that of overall survival 22.8% (SE 5%) for the whole group. In the 1996 treatment of children with relapse of ALL was unified according to theGerman protocol ALL-REZ BFM 96. Twenty-six (47.3%) out of 55 children achieving second remission were treated by chemotherapy alone, 21 (38.2%) children underwent allogeneic stem-cell transplantation (SCT), and 8 patients (14.5%) autologous SCT. Very early and early relapses were diagnosed in 78.8% of the patients. EFS was 6.7% and 18.2% for children with very early and early relapse, respectively. Significantly better results were achieved in children with late relapses (EFS 37.8%). Isolated bone marrow relapse was the most frequent type of disease recurrence (70.6%) characterized by a poor outcome (EFS 11.5%). On the other hand, more than half of boys with isolated testicular relapse were cured. SCT did not improve the prognosis of children with very early and early relapses significantly. Late relapse is heterogenous disorder. SCT has a key role in the management of selected groups of patients. For the entire group of children with late relapses the results of SCT and chemotherapy were comparable. The best treatment strategy lies in prevention of relapse through effective initial therapy of leukemia and individualization of the treatment plan according to the level of minimal residual disease.

        Key words: acute lymphoblastic leukemia, relapse, children, stem-cell transplantation, chemotherapy, BFM protocol