During a 14-year period (1980-1993) second primary lung cancer or relapse was treated in 44 consecutive patients. Thirty-seven patients had synchronous (n = 18) or metachronous (n = 19) second primary lung cancer. Ten synchronous tumors were ipsilateral and treated contemporarily with five pneumonectomies, three lobectomies and two double wedge resections. The bilateral synchronous lesions (8 patients) were treated by staged bilateral thoracotomy (mean interval; 2 months). The first resection consisted of a lobectomy in six patients and wedge resection in two. The second one was a wedge resection in six patients and a lobectomy in two. In the metachronous presentation 15 patients (79%) were asymptomatic and detected by follow-up chest X-ray. In this group the first operation was a lobectomy in 12 patients, a wedge resection or segmentectomy in 6 and a pneumonectomy in 1. The second one was a wedge resection in nine patients, a lobectomy in six and completion pneumonectomy in four. Seven patients, all of them asymptomatic, had local recurrence from their primary lung cancer. The first lung resection was a lobectomy in five patients and a wedge resection in two. The second one was completion pneumonectomy in five patients and completion lobectomy in two. We had no operative death. The actuarial over-all 5-year survival rate after the second pulmonary resection for second primary lung cancer was 38.3% with a median survival time of 13.5 months. The synchronous presentation had a better survival than the metachronous one (46.2% and 25.9%), respectively). The actuarial overall 5-year survival rate for patients with relapse was 38.1% with a median survival time of 37 months. We may conclude that an aggressive surgical approach is safe, effective and warranted in patients with either a second primary lung cancer or relapse from their primary lung cancer. Moreover, for early detection of the second lesions, follow-up at a maximum of 6-monthly intervals should be continued for more than 5 years after the first resection.