Of 99 patients with acute lymphoblastic leukemia in first bone marrow or isolated CNS relapse seen between 1968 and 1980, 48 were treated without standardized protocol and 51 according to a relapse protocol. Of 16 patients with bone marrow relapse after cessation of the initial treatment 6 survived 8 1/2 years or more, of 66 with bone marrow relapse while on therapy only 4 survived. All of the latter were low risk patients with an initial WBC of less than 20 x 10(9)/l and no enlargement of the mediastinum. All of the 17 patients with isolated CNS relapse died. The relapse protocols used probably improved the chances of children with first bone marrow but not of those with isolated CNS relapse.