In light of the transplant community's efforts to increase living donation, preserving donor autonomy is essential. Understanding how often and the reasons why potential living kidney donors opt out of the donor evaluation process for nonmedical reasons is important for assessing donor voluntariness. The experiences of individuals who opt out of donation may reveal avenues for enhancing donor protections and identify modifiable deterrents to donation. A limited number of centers have reported rates of opting out between 0.2% and 22%; the reasons for declining to donate are not well studied. This article calls for further research on potential living donors who opt out of donation. We describe challenges to studying this population and offer a roadmap for an ethical approach to conducting research on individuals who withdraw from living kidney donor evaluation.