The purpose of the study was to look at the occurrence, predictors, and consequences of unexpected early postoperative readmission after lung resection for non–small cell lung cancer. The National Cancer Database collected data on patients receiving surgery for clinical stage I to III non–small cell lung cancer. The researchers used regression models to find predictors of 30-day readmission and investigate the link between unplanned readmission and 30-day and long-term survival. Between 1998 and 2010, 129,893 individuals with stage I to III non–small cell lung cancer had a resection. Within 30 days, 5,624 (4.3%) were readmitted unexpectedly. In a multivariate regression model, unexpected readmissions were linked to increasing age, male gender, preoperative radiation, and pneumonectomy (odds ratio, 1.77; 95% CI, 1.56-2.00). Readmission was also predicted by a longer index hospitalization and a higher Charlson comorbidity score. Readmitted patients had a higher 30-day mortality rate (3.9% vs. 2.8%), as well as a higher 90-day mortality rate (7.0% vs. 3.3%, both P<.001). In a multivariate Cox proportional hazards model of long-term survival, older age, a higher Charlson comorbidity score, and a higher pathologic stage (hazard ratio, stage III 1.81; 95% CI, 1.42-2.29) were all linked to a higher risk of death. Unplanned readmission was linked to a greater risk of long-term death on its own (hazard ratio, 1.40; 95% CI, 1.34-1.47). Patients readmitted had a considerably shorter median survival time (38.7 vs. 58.5 months, P<.001). Unplanned readmissions are not uncommon after resection for non–small cell lung carcinoma. Such occurrences are linked to a higher risk of short- and long-term mortality. With a renewed national focus on readmissions and the prospect for financial penalties, more resources are needed to identify patients at risk and devise ways to prevent the negative consequences that come with them.