• OCD as current primary diagnosis

• Age 18 and older

• Yale-Brown Obsessive-Compulsive Scale (YBOCS) score of 16 or higher.

• Insufficient response to state-of-the art exposure therapy with response prevention (ERP) and/or drop-out from ERP due to extreme anxiety/avoidance

• The following comorbid disorders are allowed (as long as OCD is the current primary diagnosis): depression, other anxiety disorders, ADHD, tic/Tourette's disorder, eating disorders, personality disorders, autism spectrum disorder (when this does not dominate the clinical profile, i.e. is not main diagnosis).

• Commitment to actively undergo intensive exposure therapy (both supervised during ERP sessions, as well as unsupervised at home)

• Unmedicated (for at least 8 weeks) or stable dosage of psychotropic medication (for at least 8 weeks), involving serotonergic antidepressants (SSRI, SNRI, clomipramine). Other psychotropic medication that is allowed (provided dosage is stably established for at least 8 weeks): methylphenidate, mood stabilizers, antipsychotic drugs

• Ability to participate in frequent treatment sessions (4 days/week, for 5 (or 6, or 7) weeks) at one of the 5 sites nearest to their home and/or work

• Ability to participate in pre-treatment MRI session (for neuronavigation) at one of the 3 academic sites nearest to their home and/or work

• Capacity for providing informed consent