We report a case of primary cutaneous large B-cell lymphoma in a 63-year-old man who exhibited two firm nodules on his right lower leg for about one year.Histopathological examination revealed a dense infiltrate of atypical, large lymphocytes with mitotic figures from the entire dermis to the subcutaneous tissue. Bottom-heavy pattern was appparent. By immunohistochemical studies, atypical lymphocytes were found to be positive for CD20 and CD79a. A monoclonal immunoglobulin heavy chain gene rearrangement by Southern blot analysis was revealed in the involved tissue. On physical examination, no superficial lymphadenopathy was observed. CT scans and Ga scintigraphy showed no evidence of malignancy. According to the REAL classification, the present case corresponded to the entity, “diffuse large B-cell lymphoma” and EORTC classification classified it as large B-cell lymphoma of the leg. Local excision and local electron beam irradiation (total 40Gy) were administered. The patient has been free of disease for 1-year of follow up. [Skin Cancer (Japan) 2000; 266-270]