Background: The 30-day operative mortality rate after thoracotomy is well documented; however, the 90-day mortality rate is not and is not part of The Society of Thoracic Surgeons database. Methods: We performed a retrospective cohort study using a prospective database of patients who underwent elective thoracotomy and pulmonary resection. Mortality rates were compared with The Society of Thoracic Surgeons database. Multivariate analysis was used to identify predictors of mortality after discharge but within 30 and 90 days. Results: There were 1,845 operative patients between January 2002 and December 2008. Mortality was defined several ways. The overall discharge mortality was 3.1%; however, 18 patients (1.0%) died after discharge within 30 days and 44 patients (2.5%) died between 31 and 90 days. Sudden death (usually because of a cardiac event) was the most common cause of death in patients after discharge before postoperative day 30 and the second most common cause in those who died after discharge between days 31 and 90. These patients were more likely to have advanced age (p = 0.004), history of hypertension (p = 0.013), and coronary artery disease (p < 0.001). Conclusions: A significant number of patients die after discharge within 90 days after pulmonary resection. The most common causes of death at home are "sudden death" and are more common in patients with a history of coronary artery disease. These patients may benefit from more diligent postoperative care. A prospective database with calls to patients and families is required to accurately obtain this information and to establish true outcomes. The Society of Thoracic Surgeons database as well as nonsurgical databases that show efficacies of medical therapy for specific ailments should consider adding 90-day mortality results. © 2010 The Society of Thoracic Surgeons.