CONTEXT Although antipsychotic treatment has recently increased, little is known about how this development has differentially affected the office-based care of adults and young people in the United States. OBJECTIVE To compare national trends and patterns in antipsychotic treatment of adults and youths in office-based medical practice. DESIGN Trends between 1993 and 2009 in visits with antipsychotics for children (0-13 years), adolescents (14-20 years), and adults (≥21 years) are described on a per population basis and as a proportion of total medical office visits. Background and clinical characteristics of recent (2005-2009) antipsychotic visits are also compared by patient age. SETTING Outpatient visits to physicians in office-based practice. PARTICIPANTS Visits from the 1993-2009 National Ambulatory Medical Care Surveys (N = 484 889). MAIN OUTCOME MEASURES Visits with a prescription of antipsychotic medications. RESULTS Between 1993-1998 and 2005-2009, visits with a prescription of antipsychotic medications per 100 persons increased from 0.24 to 1.83 for children, 0.78 to 3.76 for adolescents, and 3.25 to 6.18 for adults. The proportion of total visits that included a prescription of antipsychotics increased during this period from 0.16% to 1.07% for youths and from 0.88% to 1.73% for adults. From 2005 to 2009, disruptive behavior disorders were the most common diagnoses in child and adolescent antipsychotic visits, accounting for 63.0% and 33.7%, respectively, while depression (21.2%) and bipolar disorder (20.2%) were the 2 most common diagnoses in adult antipsychotic visits. Psychiatrists provided a larger proportion of the antipsychotic visits for children (67.7%) and adolescents (71.6%) than to adults (50.3%) (P < .001). From 2005 to 2009, antipsychotics were included in 28.8% of adult visits and 31.1% of youth visits to psychiatrists. CONCLUSIONS On a population basis, adults make considerably more medical visits with a prescription of antipsychotics than do adolescents or children. Yet antipsychotic treatment has increased especially rapidly among young people, and recently antipsychotics have been prescribed in approximately the same proportion of youth and adult visits to psychiatrists.