Because long-term opioid use has been linked to the length and strength of an initial prescription, 33 states, Medicare, and some private insurers have set limits on the duration of new opioid prescriptions. In May 2017, New Jersey implemented a statewide 5-day limit on new opioid prescriptions and Penn Medicine implemented an Electronic Medical Record (EMR) alert to notify prescribers when a prescription exceeded the limit and provide compliant prescription orders. This study compared outcomes in Penn Medicine outpatient practices in New Jersey with its practices in Pennsylvania not subject to the law. Outcomes included total opioid dose and number of tablets per prescription as well as rates of prescription refills, health care visits, and telephone calls within 30 days to account for potential unintended consequences.