Previous NIH funded Attention Deficit Hyperactivity Disorder (ADHD) trials in children found that daily stimulant therapy produced sustained growth deficits. However, no federally funded studies have examined the growth suppression associated with modern once a day stimulant medications. Therefore, this study will precisely estimate the risks of stimulant induced growth suppression (SIGS), examine the underlying mechanisms and develop treatments for it. While drug holidays and caloric supplementation are two common treatments for SIGS, there has been little systematic investigation of either. It is unknown if they are effective or feasible. Therefore, using a randomized adaptive design, we will evaluate the efficacy and feasibility of these two practices vs. routine monitoring of growth in 180 prepubertal children with ADHD. An additional 50 subjects will be treated solely with behavioral therapies to evaluate for growth abnormalities associated with ADHD. The study will assess will the risk of SIGS with ER stimulants and the underlying mechanisms while providing evidenced-based treatments for its management.