The disease-free, postresection, 2 year survival rate of patients with T1 N0 non-small cell lung cancer surgically/pathologically staged by the Lung Cancer Study Group is about 82%. This study of the rate of cancer recurrence and histopathologic types is based on 572 eligible patients who submitted to complete resection of T1 N0 lung cancer and rigorous, systematic mediastinal lymph node sampling. The initial pathologic interpretation and staging were reviewed by pathologists of the Lung Cancer Study Group Pathology Reference Center to assure uniformity. Review was completed for 82% of patients included in this report. Postoperative cancer recurrence was observed in 107 of the 572 eligible patients. Histopathologic classification was squamous carcinoma (226 patients) or nonsquamous, non-small cell carcinoma (346 patients). Cancer recurrences are more frequent and recurrence rates are higher in the patients with nonsquamous cancer. There is a greater probability of first recurrence in the brain in the nonsquamous carcinoma group. This study substantiates the observation that lung cancer recurrences are histopathologically dependent in the T1 N0 subgroup of Stage I non-small cell lung cancer, with higher rates occurring among patients with nonsquamous carcinoma.