OBJECTIVES: To identify the extent to which psychotropic medication prescribing for bipolar spectrum disorders differs for younger children as compared with older children. Identifying if younger children receive similar diagnoses and treatments as older children is important, as this may inform clinical trial designs and the degree to which medication use in older children can be generalized to younger children.   METHODS: A retrospective cohort was constructed using 2005-2007 MarketScan data. Patients under 18 years of age, with one inpatient or two outpatient insurance claims for any bipolar spectrum disorder were included. Patients whose pharmacy data were unavailable or who were not continuously insured from diagnosis to 30 days after diagnosis were excluded. Ages 9 and under were considered "younger" and ages 10-17 were considered "older." Medication use was summarized as therapies prescribed within 30 days after the last bipolar diagnosis. Psychotropic medication use included lithium, anticonvulsants, antipsychotics, antidepressants, or stimulants. RESULTS: Approximately 11,000 children were eligible for inclusion in each study year. In 2007, 64.1% of younger and 62.8% of older children received psychotropic medications for bipolar disorder. Younger children were less likely than older children to receive lithium (8.2% versus 11.6%), anticonvulsants (36.2% versus 45.2%), or antidepressants. However, younger children were more likely than older children to receive antipsychotics (65.7% versus 53.1%) and stimulants (45.0% versus 29.9%). Between 2005 and 2007, psychotropic medication use changed within the younger age group, with anticonvulsant use decreasing by nearly 10% and stimulant use increasing by 7%. CONCLUSIONS: Psychotropic medication use is prevalent in both younger and older children with bipolar spectrum disorders. Younger children are significantly more likely to receive antipsychotics and stimulants as compared with older children, and less likely to receive lithium, anticonvulsants, or antidepressants.