Fluoxetine (Prozac®) has been reported to have equivalent efficacy and less side effects compared to the tricyclic antidepressants. It has become a new trend in the treatment of major depressive disorder since 1980's. Efficacy of fluoxetine has been shown not only in major depressive disorder, but also in obsessive compulsive disorder, panic disorder, bulimia nervosa, premenstrual dysphoric disorder, obesity, premature ejaculation, pain syndrome and other medical/psychiatric diseases. Fluoxetine is known to have more activating or stimulating effect than other selective serotonin reuptake inhibitors, which might be beneficial in treating the atypical feature of depression. It is also effective in diminishing appetite and carbohydrate craving. However, this effect is belived to be transient. Regarding the adverse effects, fluoxetine has the lower risk of discontinuation syndrome in comparison with other antidepressants, due to its long half-life. However, long half-life can be problematic when adverse effects become intolerable. Caution should be made when there is a possibility of drug interaction especially in the elderly. When it is prescribed to children and adolescents, monitoring for suicidal intent should be made.