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.