Obsessive‒compulsive disorder（OCD）is fairly common, with prevalence estimates ranging from 1 to 2％. OCD is generally described as having a chronic course with periods of waxing and waning of symptoms, and most individuals with OCD are at risk for other comorbid psychiatric disorders such as major depression. It is associated with considerable impairment and disability, in that individuals with OCD often experience severe social and interpersonal difficulties, familial dysfunction, occupational problems and impaired quality of life. Indeed, WHO classifies OCD as one of the top 10 most debilitating illnesses.
 Despite the proven effectiveness of cognitive‒behavioral therapy（CBT）and selective serotonin reuptake inhibitors（SSRIs）in the treatment of OCD, these 2 treatment strategies have demonstrated inadequate responses in at least 40％ of OCD patients. Moreover, even when the best available treatments are applied, a number of patients remain severely affected and experience treatment‒refractory OCD. Long‒term follow‒up（up to 40 years）studies also suggest that OCD often results in a chronic and lifelong condition with low rates of remission and with a relatively high probability of relapse. Thus, a“treatment‒refractory”status should be assessed in each OCD individual according to responses to all available therapeutic alternatives, along with the long‒term course and outcome.
 For further exploration of the treatment strategies for OCD patients assessed as“treatment‒refractory”, definition of the condition as well as the optimization and standardization of the currently best available treatments is needed. In particular, taking into account the psychopathologically and biologically heterogeneous nature of OCD, optimal and rational treatment strategies should be independently examined for each distinct OCD subtype. Further advance of social support and educational systems may also be helpful to promote earlier intervention for the treatment of individuals at high risk of developing chronic or treatment‒refractory OCD.