Strategy for lymphadenectomy in lung cancer three centimeters or less in diameter We have surgically treated 221 patients with a primary lung cancer 3.0 cm or less in diameter. There were 8 patients with a tumor 1.0 cm or less in diameter (group A), 84 with a tumor 1.1 to 2.0 cm in diameter (group B), and 129 with a tumor 2.1 to 3.0 cm in diameter (group C). The incidence of N0, N1, and N2 disease was 100%, 0%, and 0%, respectively, for patients in group A; 83%, 5%, and 12% in group B; and 62%, 12%, and 25% in group C (N0 versus N2, p less than 0.01). For the 63 patients with regional lymph node involvement, "skipping" metastasis was present in 28.6%. The 5-year survival rate was 80% for group A, 74% for group B, and 51% for group C (group B versus group C, p less than 0.01). Of the 121 patients who underwent complete resection and were followed up for 5 years, 41% had recurrence, 8% with local recurrence and 33% with distant metastasis. Therefore, it is important to do as complete a resection as possible together with mediastinal lymphadenectomy. Efforts to detect systemic spread should be made at the time of preoperative evaluation, even when the lung tumor is small. 