OBJECTIVE: To estimate the direct (medical and prescription drug) and indirect (work loss) costs of children treated for attention-deficit/hyperactivity disorder (ADHD) and their family members. METHOD: The data source was an administrative database from a national, Fortune 100 manufacturer that included all medical, pharmaceutical, and disability claims for beneficiaries (n > 100,000). The analysis involved four samples. The ADHD patient sample included individuals age 18 or younger with at least one ADHD claim during the study period (1996-1998). Resource utilization of ADHD patients was contrasted with a matched control sample of patients who did not have claims for ADHD. The ADHD and non-ADHD family samples included non-ADHD family members of ADHD patients and their matched controls. RESULTS: The annual average expenditure (direct cost) per ADHD patient was $1,574, compared to $541 among matched controls. The annual average payment (direct plus indirect cost) per family member was $2,728 for non-ADHD family members of ADHD patients versus $1,440 for family members of matched controls. Both patient and family cost differences were significant at the 95% confidence level. CONCLUSIONS: ADHD imposes a significant financial burden regarding the cost of medical care and work loss for patients and family members.