Background: Investigations of cognitive disturbances among patients with mood disorders have yielded inconsistent results. Although marked neuropsychologic deficits have been reported in elderly patients and in midlife patients with severe depression, the severity of cognitive impairments in medically healthy younger ambulatory adults with depression has not been well characterized. Methods: A comprehensive battery of standard neuropsychologic tests and experimental computerized measures of cognitive functioning were administered to unmedicated ambulatory younger adults with mild to moderate nonbipolar depression and to a group of age- and gender-equated healthy subjects. Results: Patients demonstrated a notable absence of widespread cognitive impairment. Deficits in executive functions were observed on the Wisconsin Card Sort Test but not on several other tests. Despite the absence of significant impairment on tests of attention, memory, and motor performance in the total sample, symptom severity and age of illness onset were correlated with poorer performance on some tests of cognitive functioning even after correction for age. Conclusions: These findings, derived from a large sample of unmedicated depressed outpatients, indicate that major depressive disorder in healthy younger ambulatory adults does not cause appreciable impairments in cognitive functioning in the absence of clinical and course-of-illness features. © 2001 Society of Biological Psychiatry.