Attention-deficit/hyperactivity disorder (ADHD) is a neurobehavioral disorder that typically begins in childhood and often persists into adulthood. ADHD is characterized by developmentally inappropriate levels of inattention and hyperactivity resulting in functional impairment in academic, family, and social settings. ADHD is the most commonly diagnosed neurobehavioral disorder of childhood, with previous reports documenting increasing trends in prevalence during the past decade and increases in ADHD medication use. National estimates of the number of children reported by their parents to have ever been diagnosed with ADHD and the percentage of children with ADHD currently taking ADHD medications were published in 2005 using data from the 2003 National Survey of Children's Health (NSCH). This report describes results from the second administration of NSCH in 2007, which indicated that the percentage of children aged 4-17 years with a parent-reported ADHD diagnosis (ever) increased from 7.8% to 9.5% during 2003-2007, representing a 21.8% increase in 4 years. The findings in this report help to further characterize the substantial impact of ADHD on families.