The objective of this chapter is to introduce the antidepressants. Depression and anxiety disorders involve variations in mood, behavior, cognition and somatic function and are amenable to pharmacological treatment. Depressive episodes are characterized by sadness, pessimism, lack of concentration, insomnia, mental slowing, feeling of guilt and worthlessness. Antidepressants used are as follows as selective serotonin reuptake inhibitors (SSRIs), selective serotonin and norepinephrine reuptake inhibitors (SNRIs), atypical antidepressants (5HT2 receptor antagonists), tricyclic and tetracyclic antidepressants, monoamine oxidase inhibitors, and newer antidepressants. This chapter covers the principles of antidepressant therapy, SSRI, and clinical pearls.