Secondary cutaneous T-cell lymphoma may present with various types of skin lesions, but rarely produces ulceration in contrast to primary cutaneous T-cell lymphoma. We report a case of malignant lymphoma of the tonsil that recurred as a giant cutaneous ulcer on the back of a 45-year-old man. Biopsy of the ulcer revealed a malignant lymphoma of diffuse, mixed-cell type. Surface marker analysis of the tumour cells showed suppressor/cytotoxic T-cell characteristics. The skin lesions were treated by electron beam therapy.