BACKGROUND This study was undertaken to investigate the patterns of lymph node spread and the frequency of involvement of noncontiguous lymph node stations in patients with nonsmall cell lung carcinoma who had complete surgical resection. METHODS All patients who had surgical resection as their sole treatment for nonsmall cell lung carcinoma during the years 1987-1990 were reviewed. All patients were treated similarly. Generally, complete mediastinal lymph node dissection was performed after resection of the primary lesion and N1 lymph nodes. Patients were assessed for patterns of involvement of N1 and N2 lymph node stations. The frequency of noncontiguous involvement of lymph nodes (involvement of N2 lymph nodes without involvement of N1 lymph nodes) was determined. Patient and tumor characteristics were assessed to ascertain whether certain factors were likely to predict this noncontiguous pattern of lymph node spread. RESULTS During the 4-year period of study, 336 patients with nonsmall cell lung carcinoma were managed with surgical resection alone. Of the 336, 100 had no involvement of lymph nodes, 108 had involvement of N1 lymph nodes only, 76 had involvement of N1 and N2 lymph nodes, and 52 had involvement of N2 lymph nodes only. Therefore, 52 of all 336 patients (15%) and 52 of 236 patients with lymph node involvement (22%) had noncontiguous lymph node spread. A review of the initial patient and tumor characteristics revealed that patients with a suggestion of enlarged mediastinal lymph nodes on preoperative computed tomography scans of the chest (compared with negative findings) and patients with T1 and T2 lesions (compared with T3 and T4) were more likely to have noncontiguous lymph node spread; the odds ratios (with 95% confidence intervals) were 2.18 (1.01-4.71) and 2.82 (1.36-5.84), respectively. CONCLUSIONS Noncontiguous involvement of thoracic lymph nodes occurred in approximately 15% of patients who had complete surgical resection of nonsmall cell lung carcinoma. This factor suggests that lack of involvement of N1 lymph nodes does not rule out mediastinal involvement and provides important information for complete surgical staging.