Brain metastases are a frequent feature of the course of non-small cell lung carcinoma (NSCLC). The potential usefulness of prophylactic cranial irradiation (PCI) has led to the search for target groups likely to derive benefit. This multivariate analysis looked for factors predictive of brain metastases in a group of stages I-III NSCLC patients under care of the thoracic oncology unit of Besançon University Hospital from 1977 to 2001. All the patients had the same follow-up. They were divided into two groups: BM+ when they had a brain metastasis as the first site of progression, whether solitary or not, and BM(-) otherwise. Variables analysed were age, gender, performance status (0-1 versus 2-3), weight-loss stage T-status, N-status, pathological type, type of treatment, administration of chemotherapy, use of cisplatin and response to treatment. Three hundred and five patients were eligible and there were 77 patients (25.25%) in the BM+ group. Median time to onset of brain metastases was 12 months (1-163 months) and median survival from the diagnosis of brain metastases was 6 months (1-65 months). Factors predictive of brain progression were age < or =62 years (RR: 2.5, 95% CI: 1.33-4.76 and P = 0.004), T4 tumour status (RR: 3.75, 95% CI: 1.72-8.21 and P = 0.0009), N2-3 (RR: 2.61, 95% CI: 1.32-5.15 and P = 0.0057), and adenocarcinoma (RR: 3.39, 95% CI: 1.78-6.46 and P = 0.0002). No aspect of treatment plays a role in the frequency of this type of metastasis. These factors predictive of brain progression could serve as a basis for the selection of patients with the aim of sitting of studies on prophylactic cranial irradiation in NSCLC.