Although historically considered rare, childhood onset bipolar disorder is now being diagnosed much more commonly. The course of bipolar disorder in adolescents appears to be more chronic and refractory to treatment than adult onset. A pattern of illness of very rapid, brief, recurrent episodes is common. According to DSM-IV-TR ‘rapid cycling’ is defined as the occurrence of at least four mood episodes in 1 year. Traditional mood stabilizers like lithium and valproate or atypical antipsychotic medications are the primary treatment options. Olanzapine, risperidone, and quetiapine are the FDA approved monotherapy options for the treatment of adults with bipolar disorder and recent open-label studies documented the effectiveness and tolerability of these agents in the management of youth with bipolar disorder. Here we report a 16 years-old adolescent with rapid cycling bipolar disorder who responded well to olanzapine monotherapy both at acute manic phase and during maintenance. He was a 16 years-old male adolescent, who was referred to our inpatient clinic with the symptoms of decrease in sleep, physically restlessness, irritability, increase in self-esteem, going away from home, spending the night at nightclubs and using illicit drugs. These symptoms were present for ten days and familiar for the parents. Parents told that for the last four years their son was depressed and withdrawn for 13-15 days and after then he quickly changed to a different personality and became restless, spending night out with friends and using some drugs, going far away from home and lost and every time found by the help of police. And after 12-13 days his energy level decreased and again he quickly turned to depressive-withdrawn phase. He was using effective dose of valproate and aripiprazole for the last three years but there was no decrease in the frequency or severity of his mood episodes. Olanzapine 5 mg/day was started and increased to 15 mg/day in our inpatient unit. Approximately in three weeks there was a marked decrease in his manic symptoms. He was discharged from the inpatient unit on olanzapine 15 mg/day treatment. The parents were told to make a life chart for mood changes to characterize the course of illness and patterns of episodes. During the follow-up for four months he was stable, he had no major mood episodes except two times of hypomania symptoms lasting two days, and once mild depressive symptoms lasting two days not filling the full criteria for hypomania or depression. Open-label trials and retrospective chart reviews support the effectiveness of olanzapine, risperidone, quetiapine and aripiprazole for pediatric bipolar disorder. However, the clinicians should be careful about the adverse effects of these agents such as significant weight gain and other metabolic problems. The development of bipolar disorder during childhood or adolescence disrupts ongoing developmental processes, including academic, social, and family functioning. Therefore, a comprehensive, multimodal treatment approach that combines psychopharmacology with adjunctive psychosocial therapies is almost always indicated for early onset bipolar disorder.