Although there are numerous methods for defining fracture-healing in clinical studies, no consensus exists regarding the most valid and reliable manner for assessing union or for determining which outcomes are most important. This article summarizes and describes methods for the clinical assessment of fracture-healing and reports results from a systematic review of prevalent definitions currently used in published clinical studies. Conventional radiography and ad hoc clinical definitions continue to be the most commonly used means of assessing fracture-healing in clinical studies. Investigators must improve upon and apply more rigorous outcome assessment in clinical trials, emphasize patient-important outcomes, and report factors that may bias estimated effects.