OBJECTIVE: Attention Deficit Hyperactivity Disorder (ADHD) is a condition that affects both children and adults. Although behavioral aspects of this disorder are well documented, little is known about associated medical costs. This study investigates the extent to which ADHD imposes a financial burden from the perspective of the beneficiary’s employer/third party payer. METHODS: The data source is an administrative claims database for the employed population of a national, Fortune 100 manufacturer. It includes medical, pharmaceutical, and disability claims for employees, spouses, dependents, and retirees for 1996-1998 (n > 100,000). The research sample consisted of individual patients with one or more medical or disability claim for ADHD (N = 1,308). Resource utilization in the ADHD sample was compared with that of a matched sample of the employer’s overall beneficiary population. The matching criteria were age, gender, state, and employment status. RESULTS: The analysis included both direct (medical and pharmaceutical) and indirect (disability and sporadic absenteeism) costs. Average annual costs were $2,172 for ADHD patients, and $730 for the matched controls. Total costs for ADHD patients were three times those for the controls. Thirteen percent of all direct and indirect costs associated with ADHD patients could be attributed primarily to the treatment of ADHD. Eighty-one percent of ADHD patients had office visits in 1998, versus forty-eight percent of the matched controls. CONCLUSION: Based on these findings, resource utilization by ADHD patients is substantially greater than that of individuals without ADHD. Increased health-care costs are due to medical interventions for ADHD and associated co-morbidities. Thus, ADHD is associated with a significant financial burden for employers.