We report on two adult patients with CD10+ positive acute lymphoblastic leukaemia (ALL) who presented with similar clinical and laboratory features and with a new chromosomal translocation: t(3;17)(q23;q21). This translocation may be involved in the formation of a new chimaeric transcription factor. Both patients shared several poor prognostic factors at presentation and an adverse clinical course. The t(3;17)(q23;q21) translocation may therefore predict a poor outcome in ALL.