We evaluated the overall survival with respect to prognostic factors in patients with brain metastases (BM) from lung cancer in order to assess the RTOG RPA (Recursive Partitioning Analysis) classification value and to perform intra-classes analyses including pretreatment and treatment-related variables. Between 1986 and 1997, 322 consecutive patients with BM from lung cancer were treated with whole-brain radiotherapy. Patients' distribution according to the RTOG RPA classes was: Class 1--13%, Class 2--67% and Class 3--20%. Prognostic value of the following variables was tested: RTOG RPA classes, performance status, age, extracranial metastases, control of the primary tumour, gender, histology, number of BM and interval from diagnosis to the development of BM. Intra-classes analyses were performed including radiation dose and surgery of BM. Median survival was 4.0 months. Median survival for RTOG RPA classes 1, 2 and 3 were 5.2, 4.0 and 2.5 months, respectively (p = 0.003). Extracranial metastases, performance status, control of the primary and RTOG RPA classes were prognostic for survival. Within class 2 higher radiation dose, female, no extracranial metastases and surgery of BM were related to the improved survival. RTOG RPA classes maintain their prognostic significance for patients with BM from lung cancer not participating in clinical trials.