High-dose thiotepa has been successfully included in a variety of condition
ing regimens for stem cell transplantation in hematological and solid neopl
asms. Toxicity of high-dose thiotepa mainly manifests as profound myeloabla
tion and some degree of liver damage. We report a case of inappropriate sec
retion of antidiuretic hormone (SIADH) in a patient with primary CNS lympho
ma who underwent therapy with high-dose thiotepa.