OBJECTIVES: Kentucky House Bill 1 (HB1) was enacted in July 2012 to address prescription drug abuse and diversion. This legislation included stronger pain clinic regulations, mandatory prescriber registration with Kentucky’s prescription drug monitoring program (PDMP) and mandatory use of PDMP data prior to issuing a new controlled substance prescription.  The purpose of this study was to assess the impact of HB1 on the concurrent prescribing of three controlled substances: an opioid (hydrocodone or oxycodone), alprazolam, and carisoprodol (OAC). This combination has been identified as a signal for  misuse and diversion. METHODS: De-identified PDMP data from July 2009 through June 2013 was analyzed to determine the number of patients who concurrently received prescriptions for OAC. Concurrent was defined as receiving prescriptions for each OAC component within 30 days.  12-month OAC totals were compared for each fiscal year (defined in KY as July 1 – June 30). Fiscal years were chosen for analysis based on the date of implementation of legislation (July 2012). Differences in mean number of patients receiving concurrent OAC prescriptions were analyzed using two-tailed t-tests for fiscal years pre and post legislation. RESULTS: The number of patients receiving concurrent OAC prescriptions for OAC during the study period were 22,423 (FY2010), 25,465 (FY2011), 22,795 (FY2012), and 15,983 (FY2013). The number of patients receiving concurrent OAC prescriptions was significantly lower (P<0.001) in FY2013 relative to FY2012. CONCLUSIONS: Implementation of Kentucky House Bill 1 was associated with a 29.9% decrease in the concurrent prescribing of a combination of CS commonly associated with misuse and diversion.  Further studies to differentiate the relative impact of pain clinic regulations from the impact of mandatory registration and use legislation are warranted to determine the effectiveness of these approaches in curbing the abuse and diversion of prescription drugs.