Article abstract—We evaluated the neuropsychological and personality profiles of 25 patients with chronic myeloge-nous leukemia treated with interferon alfa (IFN-α). This group of persons performed well below expectation on tests of cognitive speed, verbal memory, and executive functions. Personality changes included depression, increased somatic concern, and stress reactions. A control group of leukemia patients not treated with IFN-α had significantly better cognitive speed and mood. The pattern of cognitive and personality changes in patients receiving IFN-α is highly suggestive of frontal-subcortical brain dysfunction.