Purpose:This study sought to develop an understanding of the magnitude and types of loads generated on craniofacial implants supporting an auricular prosthesis. Materials and Methods:Strain gauges were used to measure the in vitro and in vivo misfit loads generated when connecting auricular-style superstructures to implants and the in vivo functional load generated during the removal and insertion of the auricular prostheses. In addition, the vertical misfit of the 11 custom-built two-implant superstructures used in the in vitro study was measured. Results:Superstructures used in the in vitro study that were considered clinically passive still had considerable preloads. In addition, the calibrated loads, which would result from the vertical misfit alone, did not account for the magnitude of the generated preloads. Conclusion:The clinical definition of misfit based on vertical distortion of the superstructure did not quantify the resulting misfit load. Measured in vivo functional loads were smaller than the misfit loads. Int J Prosthodont 2004;17:267–273.