We report a rare case of the plasma cell variant of Castleman's disease confined to the leptomeninges in a 42-year-old female. Flow cytometry demonstrated a minor monoclonal kappa light chain population, and conventional Southern blotting confirmed clonal rearrangement of the J(H) immunoglobulin heavy-chain gene. Polymerase chain reaction for Epstein-Barr virus and Kaposi's sarcoma-associated herpes virus was negative. The patient is disease-free five years after surgical resection. To our knowledge, clonal gene rearrangement has not been previously reported in the plasma cell variant of localized intracranial Castleman's disease.