Diaziquone (aziridinylbenzoquinone, AZQ) was given by 30-min infusion at 25 mg/m2/day on a daily x 5 schedule to 16 children with acute lymphoblastic leukemia (ALL) in bone marrow relapse, 16 children with acute nonlymphocytic leukemia (ANLL) in bone marrow relapse, and 1 child with chronic myelocytic leukemia in blast crisis. None of the children achieved bone marrow remission. Five children (four with ALL and one with ANLL) were also evaluable for the response of central nervous system leukemia; all had a significant reduction in the cerebrospinal fluid blast count. Mild transient transaminase elevation was commonly seen. Grade 3 and 4 hyperbilirubinemia was seen in association with sepsis. AZQ was ineffective for induction of bone marrow remission as utilized in this study.