We describe a BCR/ABL rearrangement positive but Philadelphia chromosome negative status in a 9-year-old boy suffering from an acute myelogenous leukaemia (AML). This case was detected in a prospective PCR screening procedure including 21 children with newly diagnosed AML and 150 children with acute lymphoblastic leukaemia (ALL). We found a 5.4% incidence of BCR/ABL rearrangement positive cases in pre-B and c-ALL in childhood.