A solitary plasmacytoma occurring in the mandible of a 15-year-old Korean male 6 years after renal transplantation is reported. The tumour presented as a hyperplastic gingival overgrowth in the right madibular molar area. Histology and immunohistochemistry revealed plasmacytoma and monoclonality of the kappa chain and IgG. In situ hybridization for Epstein-Barr virus encoded RNA (EBER) showed positive signals in the tumour cells. The tumour regressed after reducing the immunosuppressive agents with concurrent radiotherapy. The patient remains in a stable condition with normal renal functions after 7 years without recurrence. This case confirms that Epstein-Barr virus associated B-lymphoproliferative disorders are still a major complication of immunosuppression.