One hundred and ninety-two evaluable patients were treated on a multicenter protocol for adult acute lymphoid leukemia to determine in a prospective randomized fashion if late intensification chemotherapy beginning after about six months of treatment would improve remission duration and survival. The complete remission rate was 60% The median remission duration from beginning of maintenance was 18.7 versus 25.9 months (P = 0.36) for standard maintenance therapy and late intensification, respectively, and the median survival from randomization was 25.8 versus 28.5 months (P = 0.94) respectively. There was a suggestion that the late intensification strategy was helpful with respect to remission duration, and this trend was sustained in long-term follow-up. However, relapse proved to be common during the earlier phases of treatment; thus, insufficient numbers of patients were available at the randomization point to conclusively address the possible value of late intensification. Intensive therapy earlier in the course of treatment should be evaluated, including transplantation in selected patients. © 1994 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.