In 2003, an estimated 4.3% (2,473,000; 95% CI = 2,338,000-2,607,000) of children aged 4-17 years were reported to have ever had an ADHD diagnosis and were taking medication for the disorder. Rates of medication treatment for ADHD varied by age and sex and ranged from 0.3% to 9.3%. Regardless of sex, the overall medication-by-age patterns were curvilinear, with prevalence of medication treatment for ADHD highest among children aged 9-12 years, compared with younger or older children. Rates of medication treatment for ADHD followed the same pattern noted for ADHD diagnosis, such that males of all ages were more likely to have a reported history of ADHD diagnosis and to currently take medication for the disorder. More males aged 6 years were taking medication for ADHD (4.3%) than females at any age. The highest rates of medication treatment for ADHD by sex and age were reported among males aged 12 years (9.3%) and among females aged 11 years (3.7%). Medication treatment rates were significantly higher among non-Hispanic, primarily English-speaking, and insured children. Geographic variability in prevalence of medication treatment ranged from a low of 2.1% in California to a high of 6.5% in Arkansas.