OBJECTIVES:   To investigate the cost of methylphenidate and atomoxetine prescribing to children and adults in a primary care patient population. METHODS:  A retrospective, cross-sectional pharmacoepidemiological study was conducted on data of a national community pharmacy group in South Africa for 2010.  All records for methylphenidate and/or atomoxetine (ATC Code N06BA) were analysed.  Patients under 18 years were labeled as children, and patients over 18 years as adults. RESULTS:   A total of 22 387 patients (70.05% children and 29.95% adults) received one or more prescriptions for methylphenidate and/or atomoxetine during 2010.  A total of 60 370 prescriptions were dispensed (75.54% to children and 24.46% to adults).  Most adult patients (43.11%) were between 19 and 29 years of age.  Nearly three-quarters of children (71.84%) were males, compared to only 55.32% of adults.  Children received on average 2.91 prescriptions during the year and adults only 2.20.  Methylphenidate accounted for 90.00% of prescriptions to children, and 94.60% to adults.  The average sales value for a methylphenidate prescription was R366.13 for children and R408.42 for adults, compared to the average cost for an atomoxetine prescription of R582.31 for children and R653.94 for adults.  There is no generic equivalent available for atomoxetine on the South African market.  The average Prescribed Daily Dose (PDD) for methylphenidate was estimated to be 26.27 (SD=15.27) mg for children and 41.86 (SD=98.57) mg for adults, and the average PDD for atomoxetine was 38.70 (SD=21.45) mg for children and 65.96 (SD=118.67) mg for adults.  No seasonal variation was observed for atomoxetine, but methylphenidate prescribing showed peaks and troughs corresponding with the June/July and December/January holiday periods. CONCLUSIONS:   The duration of treatment and complexity of ADHD treatment is growing, extending into adulthood.  Comprehensive cost studies into adult ADHD are needed that include quality-of-life and productivity factors.