The presence of microscopic deposits of tumour cells at the bronchial resection margin (BRM) may adversely affect the prognosis of patients. Residual tumour cells were identified at the BRM in 40 (5.4%) of 735 patients who had been operated on for non-small cell lung carcinoma (NSCLC). The extent of disease was stage I in 7 (17.5%), stage II in 21 (52.5%), stage IIIa in 10 (25%) and stage IIIb in 2 (5%) patients. Malignant cells were found to have infiltrated the submucosal lymphatics in 5 (12.5%) cases and the peribronchial tissue in the remaining 35 (87.5%). Fifteen (37.5%) patients received adjuvant radiotherapy (RT). Recurrence of the disease was diagnosed in 29 (72.5%) patients after a median of 17 months (range 3-111). The recurrence was local in 17 (59%) and distant in 12 (41%). The 5-year overall actuarial survival rate was 21.6% and was not affected by RT (P = NS). Only patients with stage IIIa disease and a positive bronchial stump had a significantly reduced 5-year survival rate compared to those with a negative stump, 0% vs 17% (P < 0.001). Tumour cells at the resection margin did not affect the survival in this cohort except those with stage IIIa disease, and the addition of adjuvant RT did not significantly affect its recurrence in patients with NSCLC.