Electroencephalograms (EEGs) were recorded from 13 unmedicated and nondepressed patients with DSM-III-R obsessive-compulsive disorder (OCD) and from 10 age-matched controls. All subjects were also administered the Wechsler Memory Scale Delayed Logical Memory and Delayed Visual Reproduction tests. Quantitative analysis of the EEG revealed lower log absolute power in the delta, beta 1, and beta 2 bandwidths for OCD patients at frontal and right-hemisphere locations. OCD patients displayed greater hemispheric asymmetries in EEG activity based on difference measures of EEG power from homologous electrode pairs, indicative of severe right hemisphere EEG hypoactivity. Standardized measures of hemispheric asymmetry for the beta 2 bandwidth accurately predicted group membership and were correlated both with poorer patient performance on the visual-spatial memory task and better performance on the verbal memory task. OCD patients were significantly impaired on the visual-spatial task, but not on the verbal memory test, relative to controls.