Obsessive-compulsive spectrum (OCS) has been conceptualized by the consideration that certain disorders characterized by repetitive thoughts and/or behaviors may be continuously related to obsessivecompulsive disorder (OCD) and suggests that such disorders may be grouped together in the same category. Based on the concept of OCS, indeed, OCD has been categorized separately from other anxiety disorders in DSM-5 and is currently conceptualized as a disorder that is characterized by having preoccupations (obsessions) and/or repetitive behaviors (compulsions). Disorders with phenomenological and psychopathological features similar to those of OCD also consist of obsessive-compulsive and related disorders (OCRD) that have been newly introduced into DSM-5. Some OCRDs such as body dysmorphic disorder are characterized by preoccupations and repetitive behaviors or mental acts in response to the preoccupation, while others are primarily characterized by recurrent body-focused repetitive behaviors (e.g. hair pulling and skin picking) and repeated attempts to decrease or stop the behaviors.In the revision of ICD-11, several new conditions such as hypochondriasis and olfactory reference disorder have been added to DSM-5 OCRDs in order to enhance clinical utility paying special attention to the fact that the ICD will be used to diagnose conditions globally in primary care and specialty settings with varied resources. Further studies should be required to systematically examine whether these goals may be achieved, especially in the clinical practice related to OCRDs de ned in DSM-5 or ICD-11.