24 children with low risk acute lymphoblastic leukemia (ALL) in first relapse were re-treated with an aggressive protocol. Therapy of the first episode had adopted two different but equivalent approaches (SAKK-ALL "low risk" 76 and CALGB protocol 7611). With one exception, relapse occurred in all children before discontinuation of therapy. complete remission was achieved in 20 of the 24 children (83%). Five of 11 children in whom the length of the second remission could be evaluated had, at the time of the cutoff, been in continuous remission for 18 to 40 months. The therapy displayed considerable toxicity. From this study it is concluded that remission is achieved in the majority of children with first relapse of ALL, but that the remission can be maintained beyond 18 months only in a few children.