A prospective, multicenter, randomized cohort trial compared the post-treatment cognitive function of patients with 1 to 3 brain metastases treated with either stereotactic radiosurgery alone (SRS) (n = 111) or stereotactic radiosurgery plus whole brain radiation therapy (WBRT) (n=102). The primary endpoint was a cognitive decline of greater than 1 standard deviation on at least 1 cognitive test between the baseline and 3-month follow-up assessments. Secondary endpoint included such variables as quality of life, intracranial failure, and overall survival. The mean age of patients was 60.6 years. The patients receiving SRS plus WBRT displayed a significantly higher level of cognitive deterioration (91.7%) as compared to those patients receiving SRS alone (63.5%) (p<0.001). In addition, quality of life was higher in the SRS alone group versus the SRS plus WBRT group (p=0.001). However, time to intracranial failure was significantly shorter in the SRS alone group compared to the SRS plus WBRT group (p<0.001). The overall survival was not significantly different between groups. While progression free survival is longer in patients whom receive WBRT, there is considerable impact on cognitive decline and quality of life as well as the lack of increased efficacy with regard to overall survival. Treatment strategy withholding WBRT should be considered in this patient population.