Chromosome studies carried out in two children with acute myeloblastic leukemia (AML, M2) showed a t(2;3)(p22;q28). This abnormality was associated with monosomy 7 and del(12)(p12) in the first patient and was found only in relapse in the second patient. Comparison with the other previously published t(2;3) suggests that this translocation is a nonrandom abnormality involving a pluripotent stem cell and occurring as a secondary chromosome abnormality in AML.