Obsessive-compulsive disorder (OCD) has been linked to altered neurological function following head trauma, encephalitis, abnormal birth events, and Gilles de la Tourette's syndrome. Abnormalities in computed tomographic scans, electroencephalograms, positron emission tomographic scans, and evoked potentials have been described in this disorder, but are neither consistent nor pathognomonic of OCD. Neurological soft signs are nonlocalizing signs of deviant performance on a motor or sensory test where no other sign of a neurological lesion is present. We studied 41 medication-free patients with OCD who met DSM-III-R criteria, as well as 20 normal controls, matched for age, sex, and handedness, on 20 individual tasks that involved fine motor coordination, involuntary movements, and sensory and visuospatial function. There were significantly more signs of central nervous system dysfunction in the OCD group, as shown by abnormalities in fine motor coordination, involuntary and mirror movements, and visuospatial function. An excess of findings on the left side of the body and abnormalities of cube drawing may suggest right hemispheric dysfunction in a subgroup of patients with OCD. Soft signs correlated with a severity of obsessions. There was also a correlation between abnormalities in visual memory and recognition on neuropsychological testing and total soft signs. These findings provided additional evidence for a neurological deficit in some patients with OCD. However, further comparisons with other psychiatric populations are needed to determine whether these findings are unique to OCD or are a property of other psychiatric disorders as well.