Objective: Anecdotal evidence suggests that prescribing of ADHD therapies among children in the U.S. decreases over the summer months when children and adolescents are out of school. Methods: We used retail pharmacy prescription data to investigate monthly and annual ADHD prescribing trends from January 2003 to October 2007 to determine if there is any variation in prescribing, especially over the summer months. The prescription data was obtained from Verispan's Vector One National (VONA), which captures nearly half of all prescription activity in the U.S. The Verispan prescription data is age-specific; thus we were able to examine monthly total prescriptions for two age groups: 0 to 17 years and 18 years and older. Results: There was a significant dip in total prescription volume in the summer months for the 0-17 age group. The magnitude of the seasonality observed between May and July ranged from a 22% to 29% decrease in total prescriptions, depending on the year. In contrast, total prescriptions in the 18 and older age group have been rising steadily since January 2003, and there is no observed seasonality. Conclusion: Our findings suggest that as many as 30% of children and adolescents use ADHD medications only during the school year and stop treatment in the summer months. Assuming that a child meets the DSM-IV-TR criteria for ADHD, taking him/her off treatment, even outside the school setting, could impair his/her ability to function in everyday life. At the same time, it provides the child with a holiday from potentially serious side effects associated with stimulant use. Further research is needed to compare these and other benefits/risks associated with discontinuing ADHD therapy during the summer months.