This proposal is a cost-effectiveness study perfectly timed to take advantage of a randomized control trial of a web-based decision support system, called CHADIS, as an educational intervention for primary care physicians in their care of children with ADHD. In phase 1 of this study, supported by the Cisco Fda., over 5,800 consenting children were screened in six Mississippi School Districts using CHADIS and over 900 children were found to be at risk for ADHD. This is clearly the largest sample of its kind. Baseline measures for the children and physicians through chart audits and surveys are in place. The intervention phase will start Fall 2009 when cost data collection can also begin if this project is funded. A sample of at least 450 families will be assessed. Although this proposed cost-effectiveness study will replicate aspects of the prior MTA project, it is unique in a number of ways. First, the children in our study are selected by systematic teacher screening which is representative of a community population rather than clinical cases that are not representative in terms of family motivation or child severity. Secondly, instead of using a research intervention completed by tertiary care center specialists, the intervention being evaluated here is based is on a web-based decision support system that is scalable and designed to be used by primary care clinicians rather than mental health specialists. Use of an early detection and primary care community intervention model will have a different and potentially greater impact on costs. All previous estimates of the economic impact of ADHD have been based on well established clinical cases seen in a variety of clinical settings. In addition, this proposed study is unique in taking a very broad view of the potential economic impact of ADHD. While health insurance data is a part of this proposal it is not limited to that domain of costs. School related data is collected for the same children. We will have baseline and control subject data regarding any reductions in class retention and unnecessary use of special class placement. We will be using standard measures to assess health related costs that may have been out of pocket and costs related to unreimbursed therapies and parental time lost from work related to intervention needs or because of school disciplinary measures such as expulsions. Furthermore, the study will be prospective and collect data from parents in time proximity to the interventions rather than an over reliance on memory of past events. This research into cost effectiveness of primary care for children with ADHD facilitated by an innovative web-based screening, diagnostic and decision support tool (CHADIS) employs technology assisting with coordination of data from schools and early detection and improved accuracy of diagnosis for children therefore having great potential benefit to all affected families. Children and families everywhere will be helped by this project if it shows that the use of CHADIS in the primary care system results, not only in better care, but is also care shown to be cost-effective. Cost savings for families, insurers, schools, systems of care and states may all result and can be documented by the proposed study.