The present invention provides a method and compositions for specifically delivering an effector molecule to a tumor cell bearing an IL-13 receptor. The method involves providing a chimeric molecule that comprises an effector molecule attached to a circularly permuted IL-13 (“cpIL-13”) that specifically binds an IL-13 receptor and contacting the tumor cell with the chimeric molecule. The compositions include chimeric molecules comprising effector molecules such as modified Pseudomonas exotoxin attached to a cpIL-13. The invention further provides vectors encoding the chimeric molecules.