Although the majority of children with acute lymphoblastic leukemia (ALL) can electively stop treatment after 2 1/2-5 years of continuous disease-free remission, 20-25% of those patients relapse after discontinuation of therapy. We treated 15 patients whose disease recurred after stopping treatment. Fourteen of them attained complete remission, but the median duration of disease-free survival was only 11 months. In this population, the site of initial relapse, bone marrow or testicle, did not influence subsequent outcome. Patients who relapsed within six months of stopping initial therapy had shorter second remissions than those who relapsed after six months. We conclude that the combination chemotherapy utilized in this study was inadequate for the control of relapsed ALL. Future programs will have to use different drug combinations or bone marrow transplantation.