Childhood central nervous system (CNS) germinoma are highly curable brain tumors characterized pathologically by varying degrees of lymphocytic infiltration. The authors present a case of a CNS germinoma with significant regression in size following surgery and administration of dexamethasone, prior to initiation of chemotherapy or irradiation. The authors speculate the possible mechanism involved in its occurrence. Perioperative corticosteroid administration in patients with CNS germinoma may obfuscate the increase in response demonstrated with various chemotherapy regimens or with irradiation in CNS germinomas.