Anxiety disorders are among the most common mental disorders. One of the most effective strategies to treat anxiety disorders is exposure therapy with or without cognitive intervention. Fear reduction in exposure therapy is similar to extinction learning. Preclinical studies suggest that extinction learning can be blocked by antagonists at the glutamatergic N-methyl-D-aspartate (NMDA) receptor, and facilitated with D-cycloserine (DCS), a partial agonist at the glycine recognition site of the NMDA receptor in the amygdala. DCS is an established antibiotic drug for the chronic treatment of tuberculosis in humans, but has only recently been investigated as an augmentation therapy for psychological treatment procedures. The review of the literature provides preliminary support for the use of acute dosing of DCS as an adjunctive intervention to exposure therapy for anxiety disorders, including specific phobia and social anxiety disorder. Negative results have recently been reported in the treatment of subclinical fears of animals. These studies suggest that DCS needs to be administered on an acute rather than a chronic dosing schedule, include sufficient time for memory consolidation, and be administered together with psychological treatment that leaves sufficient room for further improvement. It remains to be seen whether these highly promising findings represent reliable pharmacological strategies to enhance exposure therapy of anxiety disorders.