Receiving trauma centers often duplicate laboratory and radiograph testing performed by referring institutions. Our objective was to quantify frequency and costs of this practice. In this prospective study of 104 consecutive interfacility-transported adult trauma patients flown by an emergency medical service to an urban level I center, flight crew noted which labs and radiographs were done at referring hospitals, which tests were sent with patients, and which were repeated on trauma center arrival. Overall, results from 246 of 283 (86.9%) laboratory tests and 241 of 249 (96.8%) radiographs done at referring hospitals were sent with patients. Repetition of laboratory tests at the receiving hospital was frequent regardless of whether initial results were sent (P = .6 by chi2), and radiograph repetition was unrelated to whether sent films were originals or copies (P = .2 by chi2). For these 104 patients, the receiving hospital charged $66,463 for repetition of work-up done at referring facilities.