Abstract Objectives Because of several recent clinical and regulatory changes regarding attention deficit−hyperactivity disorder (ADHD) in the United States, we quantified changes in the diagnosis of ADHD and its pharmacologic treatment from 2000 through 2010. Methods We used the IMS Health National Disease and Therapeutic Index, a nationally representative audit of office-based providers, to examine aggregate trends among children and adolescents younger than 18 years of age. We also quantified how diagnosis and treatment patterns have evolved on the basis of patient and physician characteristics and the therapeutic classes used. Results From 2000 to 2010, the number of physician outpatient visits in which ADHD was diagnosed increased 66% from 6.2 million (95% confidence interval 5.5−6.9M) to 10.4 million visits (95% confidence interval 9.3−11.6 million). Of these visits, psychostimulants have remained the dominant treatment; they were used in 96% of treatment visits in 2000 and 87% of treatment visits in 2010. Atomoxetine use decreased from 15% of treatment visits upon product launch in 2003 to 6% of treatment visits by 2010. The use of potential substitute therapies—clonidine, guanfacine, and bupropion—remained relatively constant (between 5% and 9% of treatment visits) during most of the period examined. During this period, the management of ADHD shifted away from pediatricians and towards psychiatrists (from 24% to 36% of all visits) without large changes in illness severity or the proportion of ADHD treatment visits accounted for by males (73%–77%). Conclusions In 10 years, the ambulatory diagnosis of ADHD increased by two-thirds and is increasingly managed by psychiatrists. The effects of these changing treatment patterns on children’s health outcomes and their families are unknown.