In adenocarcinoma of the esophagus or gastroesophageal junction, little attention has been paid to the biologic significance of extracapsular lymph node involvement (LNI). In the present study, a consecutive series of 251 patients with lymph node dissemination were reviewed. All patients underwent esophagectomy for adenocarcinoma and were prospectively followed. A total of 1562 positive lymph nodes were reexamined. Extracapsular LNI was identified in 456 lymph nodes (29%) in 166 patients (66%). Extracapsular LNI was confined to one lymph node in 63 patients (38%). The occurrence of extracapsular LNI increased significantly with the depth of invasion, presence of positive resectable truncal nodes, number of resected nodes, number of positive nodes, and lymph node ratio. The median potential follow-up period was 58 months (range, 12-143 months). In this period, 178 patients died of recurrent disease. The pattern of recurrence was comparable between patients with and without extracapsular LNI (P = 0.938). The median survival in patients with extracapsular LNI was 15 months (95% confidence interval, 12-18 months) compared with 41 months (95% confidence interval, 19-64 months) in those without extracapsular LNI (P < 0.001). Median survival of patients with 2 or more lymph nodes was 12 months (95% confidence interval, 8-15 months). Multivariate analysis demonstrated that T-stage, extracapsular LNI, and lymph node ratio were independent prognostic factors. The presence of extracapsular LNI identifies a subgroup with a significantly worse long-term survival. Together with the T-stage and the lymph node ratio, extracapsular LNI reflects a particularly aggressive biologic behavior and has significant prognostic potential.