The Asian variant of intravascular large B cell lymphoma is a special type of intravascular lymphoma with hemophagocytic syndrome and hypercytokinemia including interleukin-6, which stimulates antidiuretic hormone synthesis in the hypothalamus. We present here that the syndrome of inappropriate antidiuretic hormone secretion frequently occurs in patients with the Asian variant of intravascular large B cell lymphoma. The syndrome of inappropriate antidiuretic hormone secretion was found in eight of 118 (6.8%) lymphoma patients at the first diagnosis. Although there were six (5.1%) among 118 lymphoma patients with the Asian variant of intravascular large B cell lymphoma, four of the six patients (66.7%) developed the syndrome of inappropriate antidiuretic hormone secretion. In four patients with the Asian variant of intravascular large B cell lymphoma with the syndrome of inappropriate antidiuretic hormone secretion, elevated serum interleukin-6 and low sodium levels were almost normalized after chemotherapy. The Asian variant of intravascular large B cell lymphoma patients frequently develop the syndrome of inappropriate antidiuretic hormone secretion, and interleukin-6 might play a role in the occurrence of this disease. We should pay attention to hyponatremia caused by the syndrome of inappropriate antidiuretic hormone secretion in patients with the Asian variant of intravascular large B cell lymphoma.