Objective: This study describes recent trends and patterns in antipsychotic treatment of privately insured children aged 2 through 5 years. Method: A trend analysis is presented of antipsychotic medication use (1999-2001 versus 2007) stratified by patient characteristics. Data are analyzed from a large administrative database of privately insured individuals. Participants were privately insured children, aged 2 through 5 years, with 12 months of continuous service enrollment in 1999-2001 (N = 400,196) or 2007 (N = 755,793). The main outcomes are annualized rates of antipsychotic use and adjusted rate ratios (ARR) of year effect on rate of antipsychotic use adjusted for age, sex, and treated mental disorder. Results: The annualized rate of any antipsychotic use per 1,000 children increased from 0.78 (95% confidence interval [CI] 0.69-0.88) (1999-2001) to 1.59 (95% CI 1.50-1.68) (2007) (ARR 1.76, 95% CI 1.56-2.00). Significant increases in antipsychotic drug use were evident for boys (ARR 1.66, 95% CI 1.44-1.90) and girls (ARR 2.26, 95% CI 1.70-3.01) and for children diagnosed with several different psychiatric disorders. Among antipsychotic-treated children in the 2007 sample, pervasive developmental disorder or mental retardation (28.2%), attention deficit/hyperactivity disorder (ADHD) (23.7%), and disruptive behavior disorder (12.9%) were the most common clinical diagnoses. Fewer than one-half of antipsychotic-treated young children received a mental health assessment (40.8%), a psychotherapy visit (41.4%), or a visit with a psychiatrist (42.6%) during the year of antipsychotic use. Conclusions: Despite increasing rates of antipsychotic use by very young children, provision of formal mental health services remains sparse. These service patterns highlight a critical need to improve the availability of specialized and well integrated mental health care for very young children with serious mental health problems. (Contains 4 tables and 1 figure.)