PURPOSE: Radiation Therapy Oncology Group (RTOG) 0118 randomized patients with multiple brain metastases to whole-brain radiotherapy (WBRT) +/- thalidomide. This secondary analysis of 156 patients examined neurocognitive and quality of life (QOL) outcomes. METHODS AND MATERIALS: Quality of life was determined with the Spitzer Quality of Life Index (SQLI). The Folstein Mini-Mental Status Exam (MMSE) assessed neurocognitive function. SQLI and MMSE were administered at baseline and at 2-month intervals. MMSE was scored with a threshold value associated with neurocognitive functioning (absolute cutoff level of 23) and with the use of corrections for age and educational level. RESULTS: Baseline SQLI predicted survival. Patients with SQLI of 7-10 vs. <7 had median survival time (MST) of 4.8 vs. 3.1 months, p = 0.05. Both arms showed steady neurocognitive declines, but SQLI scores remained stable. Higher levels of neurocognitive decline were observed with age and education-level corrections. Of patients considered baseline age/educational level neurocognitive failures, 32% died of intracranial progression. CONCLUSIONS: Quality of life and neuropsychological testing can be prospectively administered on a Phase III cooperative group trial. The MMSE should be evaluated with adjustments for age and educational level. Baseline SQLI is predictive of survival. Despite neurocognitive declines, QOL remained stable during treatment and follow-up. Poor neurocognitive function may predict clinical deterioration. Lack of an untreated control arm makes it difficult to determine the contribution of the respective interventions (i.e., WBRT, thalidomide) to neurocognitive decline. The RTOG has developed a trial to study the role of preventative strategies aimed at forestalling neurocognitive decline in this population.