Current therapeutic options for treating depression are limited to use of antidepressants that target the monoamine system (serotonin, dopamine, epinephrine). Despite their effectiveness in treating depression, they have several downsides. The main problems are that they require weeks, sometimes months to reach their maximum efficacy and have limited effect in certain patients with treatment-resistant depression. Glutamate receptors are emerging as a new promising target for future antidepressant drugs. In this article we will discuss the potential of treating depression with an N-methyl-D-aspartate receptor antagonist – ketamine. The studies we review have focused on ketamine’s fast effect on treating depression symptoms, length of its effect, adverse effects, and efficacy of treating treatment-resistant depression.