Spontaneous regression of diffuse B-cell type lymphoma of the lumbar vertebra is reported. A 61-year-old woman experienced spontaneous disappearance of a large psoas mass associated with an infiltrating process of the lumbar vertebrae. The biopsy of the residual change after spontaneous regression revealed reactive foamy histiocytes and small lymphocytes with no atypia. The lesion recurred 7 months later with no systemic treatment in the interim, when the diagnosis of lymphoma was finally made. Spontaneous regression may be related to potentiation of the host immune response, which affects tumor growth.