BACKGROUND The estimated prevalence of Attention Deficit Hyperactivity Disorder (ADHD) reported in European countries is 2 to 5% of school age children. Political concern has been expressed in Switzerland about possible over treatment with methylphenidate. The purpose of this research, commissioned by the regional public health authority, was to assess the prescription of methylphenidate (Ritalin) for children as a treatment of ADHD. METHODS The regional health authority collected all prescriptions of Ritalin delivered in pharmacies during 2002. Data available from prescriptions and analyzed were: age, sex and place of residence of the patient, dosage prescribed, date of prescription, place of practice and medical specialization of doctors. Only patients living in the canton of Vaud and aged less than 20 years were included in the analysis. RESULTS Six hundred and ninety-seven patients, aged less than 20 years, received Ritalin in 2002. The mean age was 12.1 years (median: 12 years; range: 3-19), 15% were female. These patients represented 0.74% of the 5-14 years old population living in the canton of Vaud. Eighty percent of patients had a prescription from a specialist (pediatrician or psychiatrist) during the year. CONCLUSIONS Less than 1% of the young population receives methylphenidate in the canton of Vaud. Dosage complies with the recommendations of the Swiss Medic Compendium. The large majority of patients receive prescriptions for methylphenidate from specialists. A new study based on the 2005 data will be conducted to follow changes in the prescription of Ritalin.