Interleukin-13 (IL-13) is a T(H)2 cytokine that plays a crucial role in the pathophysiology of tumors and favor tumor growth and recurrence by negative regulation of tumor immunosurveillance. In the present investigation, we have determined the IL-13 level in the serum and ascitic fluid of the DL-bearing host and the possible source of IL-13 in the ascitic fluid. IL-13 level was elevated in serum and ascitic fluid of host bearing a transplantable T-cell lymphoma. DL cells as well as tumor-associated macrophages express and secrete IL-13 in the milieu, which provide further insight for DL-induced immunosuppression in a tumor-bearing host.