The symptoms of obsessive-compulsive disorder (OCD)--repetitive troublesome intrusive thoughts and/or compulsions--may indicate a reduction in the efficiency of inhibitory control over thought and action. A number of neuropsychological studies using various indices of inhibitory activity were aimed at verifying the hypothesis of deficient inhibition in OCD. The paper critically reviews the studies that relate to three kinds of inhibition-related phenomena --i.e. negative priming, thought suppression, and directed forgetting--and summarises the results of other research addressing the inhibitory processes in OCD subjects. All in all, the results do not support the hypothesis of general inhibitory deficit in OCD, although some studies suggest an impairment in the ability to suppress specific mental contents in this clinical group. In the discussion some general problems related to neuropsychological diagnosis of inhibitory processes in psychopathology are indicated.