The preferred bonding site of Sb on Si(100) is investigated using transmission ion channeling. A Monte Carlo simulation that includes a model for channeled ion energy loss has been used to calculate scattering yields and energy distributions for trial adatom sites. A method of data collection and analysis was developed to use the calculated scattering yields and energy distributions for quantitative site determination. The Sb site thus found agrees well with previous experiments on this system, namely, the Sb is in a modified bridge site with a bond length of 2.80 +/- 0.10 Angstrom and a distance above the bulk-extrapolated silicon surface of 1.63+/-0.10 Angstrom. However, the vibrational amplitude necessary for the simulated energy distributions to match experiment is anisotropic, apparently in contradiction with other results. A possible resolution is proposed.