Magnetic resonance imaging of the brain was undertaken in women with obsessive-compulsive disorder (n = 13), trichotillomania (n = 17), and healthy controls (n = 12). Caudate volume and ventricular-brain ratio (VBR) (variables that have previously been highlighted as abnormal in studies of OCD) were compared in the three subject groups and were correlated with neuropsychological and neurological soft sign findings. No significant differences were found between women with OCD, trichotillomania and normal controls on caudate volume or VBR. Decreased left caudate volume was significantly correlated with impairment on neuropsychological testing and with increased neurological soft signs. The negative findings here may indicate that in women with OCD and related disorders structural brain abnormalities are less obvious or less common than in men with these conditions, or they may reflect inadequate sensitivity of the brain measures employed.