Post transplant lymphoproliferative disorder (PTLD) is the commonest form of post transplant malignancy in children. The incidence in renal transplant recipients varies between 2%-4%. They are characterized by uncontrolled B lymphocyte proliferation, in most cases driven by Epstein Barr virus (EBV). They are more common in younger children, EBV seronegative patients and those who receive aggressive immunosuppression. PTLD commonly presents in an unspecific form and it requires high suspicion rate for its diagnosis, especially in children with risk factors. We report a twelve year-old girl who developed fever, sore throat and lymph node enlargement, six months after receiving a renal allograft. Laboratory assessment and imaging studies were compatible with PTLD, which was confirmed by biopsy. Treatment was reduction of immunosuppression and surveillance. The patient had a favourable evolution (Rev Med Chile 2009; 137: 405-10).