Between 1978 and 1989,44 patients underwent 44 thoracotomies and 55 craniotomies for nonsrnall cell lung carcinoma (NSCLC) and its brain metastases. Patient ages ranged from 20 to 75 years. There were no intraoperative mortalities. The 2-, 3-, and 5-year survival rates following the initial craniotomy were 23%, lo%, and lo%, respectively. Patient survival did not differ with respect to solitary or multiple metastases or the sequence of surgery for primary lesion and brain metastases. Moreover, there was no significant difference in survival between patients treated by surgery alone and those receiving surgery followed by whole brain radiotherapy. After 1985, in vitro tissue culture was attempted using freshly resected specimens of brain metastases obtained from 30 consecutive cases. Of those specimens, nine (30%) were successfully established as permanent cell lines. Eight of those cell lines revealed DNA-aneuploid pattern on flow cytometric analysis. The remaining cell line was not analyzed. Karyotype analysis was also performed in eight of nine established cell lines. Two adenocarcinoma cell lines showed the presence of +3p-chromosome, and three showed +7qchromosome as recurrent chromosomal abnormalities. These findings provide new evidence concerning the presence of 3p-and/or 7q-marker chromosomes in certain adenocarcinoma cell lines established from brain metastases. The prognosis was poorer in the group with in vitro tumor growth than that in the group showing no in vitro tumor growth. These cell lines established from brain metastases may be useful materials not only for studying the biological characteristics and chemo-sensitivity testing, but also for estimating prognoses after resection of brain metastases.