Gender variation in diagnosis and treatment of ADHD is well documented: boys are more likely to be diagnosed and receive pharmacologic treatment than girls. However, little is known about gender variation in the quality (dosage and persistence) of pharmacologic treatment received by ADHD-diagnosed children. OBJECTIVE: To examine gender variation in intensity and persistence of psychostimulant treatment among a national, population-based sample of ADHD-diagnosed children. METHODS: We analyzed medical and pharmaceutical claims in the Medical Expenditures Panel Survey (MEPS) from January 1 through December 31, 1998 among all ADHD-diagnosed children (N=195) aged 4-19years. Psychostimulant doses were converted to Methylphenidate Equivalent Units (MEU) according to previously published research (MEU: 20 mg Methylphenidate=10 mg dextroamphetamine=10 mg amphetamine salts=56.25 mg Pemoline). Doses were classified as high (>15.0 mg MEU), medium (5.0 - 15.0 mg MEU), or low (<5.0 mg MEU). Persistence of treatment was determined by number of prescription fills (PF) in a calendar year. Separate weighted logistic and multiple regression analyses were conducted with MEU and PF as dependent variables respectively. RESULTS: As has been reported previously in the literature, males were 1.3 (+/-0.004) times more likely to receive a prescription for psychostimulants (p <0.001). However, among those receiving any psychostimulant, females were 1.2 (+/-0.008) times more likely than males to receive high doses (p <0.001). There was no difference in persistence of psychostimulant treatment by gender. CONCLUSION: Whereas girls with AD/HD were less likely to be treated with psychostimulants, once treated, they received higher doses. Further research is required to confirm whether such gender disparities persist, and, if so, whether they are justified. Additional research linking quality with outcomes of care are necessary to determine their effects on the outcomes of children with ADHD. In this way, researchers and clinicians can work together to translate findings into better patient care.