OBJECTIVES: To examine and describe gender differences in psychoactive medication treatment for AD/HD in a population-based cohort. METHODS: Medical and school records of all children born (N=5718) in Rochester, MN 1976-1982 were reviewed to identify those with AD/HD (N=375). All psychoactive medications (psychostimulants [STIM], centrally acting alpha-adrenergic agonists [CAA] and/or tricyclic antidepressants [TCA]), doses prescribed, start and stop dates, and subtype of AD/HD clinical diagnosis were abstracted. Psychostimulant doses were converted to Methylphenidate Equivalent Units (MEU: 20mg methylphenidate=10mg dextroamphetamine=10mg amphetamine salts=56.25mg pemoline). RESULTS: Boys with AD/HD were more likely than girls to be treated with STIM, either alone or in combination with TCA and/or CAA (80.8% vs 69.1%, OR 1.9, 95% CI 1.1-3.2, p=0.020). However, boys and girls were equally likely to be treated with STIM alone (66.2% versus 63.8%, OR 1.1, 95% CI 0.7-1.8, p=0.68). Mean age at treatment onset was similar (boys 10.3 years, girls 10.7 years, p=0.46). Median treatment duration was 34 months (mean=42.0, SD=37.1), with no gender difference. Median average daily dose of STIM was 21.3 mg MEU (mean=24.4mg, SD=11.0mg). Boys received significantly higher average daily doses than girls (median 22.5 vs. 20.0mg MEU; p=0.002). Treatment started significantly earlier for combined (9.7 years) and hyperactive-impulsive subtypes (10.0 years) than for the inattentive type (12.7 years). Treatment duration was significantly longer for combined (40.5 months) than for either hyperactive-impulsive (22.6 months) or inattentive subtype (19.1 months). The gender differences in AD/HD treatment described above could not be accounted for by gender differences in AD/HD subtype. CONCLUSIONS: Boys with AD/HD were more likely to be treated with psychostimulants, and received significantly higher doses of psychostimulants, suggesting disparities in AD/HD treatment between boys and girls that may affect quality of care.