Incompleteness-the troubling and irremediable sense that one's actions or experiences are not "just right"--appears to underlie many of the symptoms of obsessive-compulsive disorder (OCD). Because incompleteness may reflect basic sensory-affective dysfunction, it presents a challenge to clinicians wishing to apply cognitive-behavioral treatments. In this article, I review ways of adapting well-demonstrated treatment principles to this condition. A case is presented and then used to discuss challenges in conducting cognitive-behavioral therapy with this population. Behavioral methods aimed at habituation (e.g., exposure and ritual prevention [ERP]) are probably more applicable than conventional cognitive techniques. However, even these may result in modest long-term gains; relapse is a probability if they are not actively practiced after treatment cessation.