Chromosomal changes are necessary in determining the classification, prognosis and using the appropriate therapeutic regimen in acute leukemia. Isochromosomes are uncommon chromosome aberations in childhood acute lymphoblastic leukemia (ALL) and the effect of i(9q) is not well established. We present an 8-year-old male case of pre-B ALL who has an unusual course at diagnosis. He was hospitalized three times in three different hospitals and blastic cells disappeared after the first hospitalization following blood transfusion without chemotherapy. In the following two hospitalizations no blastic cell was observed and transfused with a pack of erythrocyte suspension each time. In the fourth hospitalization, bone marrow aspiration revealed L1 type of lymphoid blast cell infiltration. The remission was achieved on the 15th day of the induction therapy and he has been in remission for the last 6 months. This unusual presentation and early remission achieved by induction therapy in this patient may support the literature that isochromosome 9q has a favourable outcome in childhood ALL. (c) 2006 Elsevier Ltd. All rights reserved.