Exposure therapy is based on well-researched fear extinction learning paradigms, where individuals confront what they fear in a therapeutic manner and learn that the feared outcome will not occur. Ressler et al's groundbreaking translational research showed that D-cycolserine (DCS), an analogue of D-alanine and a partial agonist at the NMDA receptor, facilitates the process of fear extinction. DCS is different from other pharmacological agents used to treat social phobia which are prescribed chronically (daily) over a period of months or years to maintain a therapeutic dose; one pill of DCS is taken immediately before exposure therapy sessions. This work sparked a flurry of research showing that DCS augments exposure therapy for a variety of anxiety disorders; people who take DCS show benefit from therapist-assisted exposure therapy more quickly than those who take placebo. Two randomized double-blind, placebo-controlled studies of social phobia conclude that the combination of DCS and therapist-assisted exposure therapy improves treatment response when participants complete fewer exposure sessions. The ability of DCS to speed up the response to exposure therapy is especially valuable for sufferers using self-guided treatment, because they are not generally compliant with the full exposure protocol. The combination of DCS and self-guided exposure therapy would increase access to effective treatment. The use of DCS with self-guided exposure, however, has never been tested.