Reducing the rate of avoidable errors is crucial to patient safety. Telephone calls with misunderstood critical results constitute one area in which opportunities for improvement exist. The aviation industry has dealt with this issue by requiring pilots to repeat instructions received from the air traffic controller. At 3 health care organizations, we tested a program to decrease telephone reporting errors by requiring the recipients of critical results to repeat the message. Of 822 outgoing telephone calls from the laboratory, 29 errors were detected (error rate 3.5%). Calls to physicians had the highest rate of errors (6/95 [5%]). The time required to ask for the information and for the message to be repeated averaged 12.8 seconds per call, which corrected 29 errors. A simple system of repeating telephoned laboratory results has the potential to reduce the risk of medical errors and improve patient safety.