Prescription stimulant use, primarily for the treatment of attention-deficit/hyperactivity disorder (ADHD), has increased among adults in the United States during recent decades, while remaining stable or declining among children and adolescents (1,2). MarketScan commercial claims data were analyzed to describe trends in prescription stimulant fills before and during the COVID-19 pandemic (2016-2021) by calculating annual percentages of enrollees aged 5-64 years in employer-sponsored health plans who had one or more prescription stimulant fills overall and by sex and age group. Overall, the percentage of enrollees with one or more prescription stimulant fills increased from 3.6% in 2016 to 4.1% in 2021. The percentages of females aged 15-44 years and males aged 25-44 years with prescription stimulant fills increased by more than 10% during 2020-2021. Future evaluation could determine if policy and health system reimbursement changes enacted during the pandemic contributed to the increase in stimulant prescriptions. Stimulants can offer substantial benefits for persons with ADHD, but also pose potential harms, including adverse effects, medication interactions, diversion and misuse, and overdoses. Well-established clinical guidelines exist for ADHD care, but only for children and adolescents* (3); clinical practice guidelines for adult ADHD could help adults also receive accurate diagnoses and appropriate treatment.