One hundred 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 was 13.5 versus 25.9 months (P = 0.31) for standard maintenance therapy and late intensification, respectively, and the median survival was 17.5 versus 34.7 months (P = 0.19) respectively. Although there was a suggestion that the late intensification strategy was helpful, relapse proved to be common during the early 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 remission should be evaluated.