We report a case of positive Philadelphia chromosome adult acute lymphoblastic leukaemia with a novel unbalanced translocation t(17;19), leading to trisomy of 17q21-qter. The patient did not obtain complete haematological response and died a few months after diagnosis. The significance of the 17q21-qter trisomy, resulting from this novel translocation, and its possible role in the progression of the leukaemia is discussed.