Abstract We present a summary of Charpy impact verification test data that were evaluated by the National Institute of Standards and Technology from January 1994 to December 1996. The Charpy impact machines that met the verification requirements of ASTM Test Methods for Notched Bar Impact Testing of Metallic Materials (E 23) are broken down by year and by reference lot. Based on the data, a proposed verification rule that limits the range of the verification set has been examined. We also present the results for determining whether two energies (lower and upper ends of the machine capacity) or three (lower, middle, and upper) are needed to verify the performance of the large-capacity impact machines; currently E 23 requires three energies to be tested.