Involvement of the inferior vena cava (IVC) by testicular neoplasms is unusual and often clinically unsuspected. We present a patient with testicular seminoma that involved the IVC secondarily and caused multiple pulmonary emboli requiring the placement of a caval filter. The radiographic features of this phenomenon are presented with special emphasis on the computed tomographic (CT) appearance of caval thrombosis and pulmonary embolus. The characteristically low density lymphadenopathy of seminoma may obscure the diagnosis of caval thrombosis on CT. Although the findings are nonspecific, tumor invasion of the IVC should be suspected in all patients with testicular neoplasms who demonstrate caval thrombosis radiographically.