The purpose of this Circular is to assist both structural and geotechnical engineers to better understand the calibration process and what information is required to perform such calibrations. The Circular describes how such calibration efforts need to be documented so that the calibration results become a heritage for future users of the AASHTO LRFD specifications and thereby enhance future LRFD research and development. There are certain places in the LRFD specifications where other methods are allowed, but users are faced with determining their own resistance factors. This Circular is intended to help standardize the  approach used to statistically characterize data for use in the calibration process. It describes how to conduct the actual calibration and, once completed, how to apply the results to the development of LRFD design specifications.