Elevated serum tumor markers in patients with testicular cancer after induction chemotherapy due to a reservoir of markers in cystic differentiated mature teratoma. Elevated serum tumor markers in patients with testicular cancer after induction chemotherapy indicate in most instances the presence of residual malignant disease. We describe 2 patients with elevated tumor markers after chemotherapy and before retroperitoneal lymph node dissection who did not prove to have residual malignant disease but cystic differentiated mature teratoma with a high content of alpha-fetoprotein and beta-human chorionic gonadotropin, respectively, in the cysts. It is postulated that leakage of the contents of these cysts to the plasma compartment was responsible for maintaining elevated serum tumor marker levels. Recognition of such entities is of consequence since unnecessary salvage chemotherapy in these patients may be avoided. 