Abstract A chemically induced, transplantable rat tumor took and grew at all sites but when conjugated with phosphorylcholine appeared to alter its antigenic configuration in such manner as to grow at sites of immunological privilege only. After chemical sympathectomy, the previously tumor-resistant tissues became receptive to grafts of tumor/phosphorylcholine conjugates. It was concluded that sympathectomy transformed the affected region into an immunologically privileged site. The implications of these findings, particularly the genesis of pulmonary cancer, are discussed.