BACKGROUND: This study assessed treatment patterns and examined organ utilization in the setting of single-lung transplantation (SLT). METHODS: The United Network for Organ Sharing database was queried for all SLTs performed from 1987 to 2011. Trends in utilization of the second donor lung were assessed, both from recipient and donor perspectives. Donors were stratified into 2 groups: those donating both lungs and those donating only 1 lung. Independent predictors of using only 1 donor lung were identified using multivariable logistic regression. RESULTS: We identified 10,361 SLTs originating from 7,232 unique donors. Of these donors, both lungs were used in only 3,129 (43.3%), resulting in more than 200 second donor lungs going unused annually since 2005, with no significant increase in use over time (p = 0.95). After adjustment, donor characteristics predicting the second donor lung going unused included B/AB blood groups (adjusted odds ratio [AOR]: 1.69 and 2.62, respectively; p < 0.001), smaller body surface area (AOR, 1.30; p = 0.02), lower donor partial pressure of arterial oxygen (AOR, 0.90 per 50 mm Hg increase; p < 0.001), pulmonary infection (AOR, 1.15; p = 0.04), extended criteria donor status (AOR, 1.66; p < 0.001), and death caused by head trauma (AOR, 1.57; p < 0.001) or anoxia (AOR, 1.53; p = 0.001). CONCLUSIONS: Among donors for SLT, less than half of all cases led to use of the second donor lung. Although anatomic, infectious, or other pathophysiologic issues prohibit 100% utilization, more aggressive donor matching efforts may be a simple method of increasing the utilization of this scarce resource, particularly for less common blood types.