Types of radiation therapy constitute the primary and most successful therapeutic approaches for postoperative patients with a variety of brain tumors (See & Gilbert, 2004). However, this treatment modality has been shown to result in neuroanatomical damage and related cognitive problems (Crossen, Garwood, Glatstein & Neuwelt, 1994). The neurocognitive changes, as well as the underlying neurological impairments that result from radiation therapy remain undefined and quite controversial (Armstrong, et al., 2000). This paper reviews the existing literature on radiation effects in general treatment populations, with a primary focus on adult brain tumor patients. Quantitative analyses of neuropsychological data prospectively collected at baseline and yearly up to eight years post-treatment is then presented in order to identify cognitive areas of apparent sensitivity, with a specific focus on memory and processing speed. Results indicate differential effects across time periods and neurocognitive domains. Consistent with what was expected given the review of literature, some cognitive measures showed a pattern of improvement followed by significant decline. However, others manifested continual trends for improvement.