BACKGROUND: There are concerns about the frequency and appropriateness of psychostimulant drug prescription to children. In order to identify unusual or unexpected patterns of use or prescribing, we reviewed prescription of methylphenidate (Ritalin) to children and adolescents aged 19 years or less in British Columbia between 1990 and 1996. METHODS: We obtained information about patients, physicians and prescriptions from British Columbia's Triplicate Prescription Program database for controlled drugs. Prescription data were available for the period Jan. 1, 1990, to Dec. 31, 1996. Linkage with the BC Linked Health Dataset provided additional demographic and health information. RESULTS: In 1990, 1715 children received at least 1 prescription for methylphenidate (1.9 per 1000 children). By 1996, the number had increased to 10,881 children (11.0 per 1000). Because some children were prescribed methylphenidate in more than 1 year, we also calculated the frequency with which the drug was prescribed to children who had never received it before. This rate increased from 1.0 per 1000 children in 1990 to 4.7 per 1000 in 1995; the rate fell in 1996 to 3.5 per 1000. The number of children receiving methylphenidate varied across health regions of the province, from 12.0 to 35.4 per 1000. Use also varied by socioeconomic status quintile: in the 2 lowest (least privileged) quintiles, 21.6 per 1000 children received methylphenidate, compared with 18.4 per 1000 in the 3 highest quintiles (relative risk 1.2, 95% confidence interval 1.1-1.2). Pediatricians and psychiatrists wrote 23% and 21% of all prescriptions respectively. General practitioners accounted for 56% of all prescriptions and 41% of initial methylphenidate prescriptions. A claim for prior specialist consultation was found in 30% of such cases. Many of the children who received more than 10 prescriptions had seen 4 or more physicians. The average daily dosage prescribed differed little among general practitioners, pediatricians and psychiatrists, unlike the mean interval between successive prescriptions: 89.9 (standard deviation [SD] 68.2), 99.8 (SD 64.1) and 75.9 (SD 70.2) days respectively. Persistence with therapy was more likely when a psychiatrist provided the initial prescription, or with involvement of more than one specialty. INTERPRETATION: Many trends and practices in the prescription of methylphenidate to children in British Columbia are consistent with other settings and accepted standards. Some aspects warrant closer investigation, including regional and socio-economic discrepancies in the distribution of patients, the relative involvement of primary and specialist care providers, continuity of care issues and time intervals between prescriptions.