Hyponatremia is one of the most common electrolyte disorders encountered in clinical practice of medical anticancer treatment. Cisplatin (CDDP) is a well-known chemotherapeutic agent that associates with hyponatremia. We retrospectively studied clinical features of hyponatremia CDDP administration. The incidence of hyponatremia at the first administration was 64. 1%. The significant risk factors of hyponatremia are body weight less than 60 kg, creatinin clearance less than 60mL/min, and sodium depletion and intake loss due to treatment-induced anorexia, nausea, vomiting and diarrhea. The mechanism of hyponatremia induced by CDDP is thought to be mainly renal salt wasting, and sometimes the syndrome of inappropriate secretion of antidiuretic hormone(SIADH).