Prescription drug monitoring programs (PDMPs) are used by local and State authorities to combat the problem of prescription drug abuse. PDMPs collect data on the number of controlled substance prescriptions dispensed from pharmacies and make it available to authorized users. This data is used by authorities to identify major sources of prescription drug diversion such as prescription fraud, forgeries, doctor shopping, and improper prescribing and dispensing. Evaluations of PDMPs have found that PDMP data can assist clinically appropriate prescribing, improve medical care, and reduce doctor shopping; use of PDMP data by third party payers can improve medical care and reduce drug and medical claims related to inappropriate prescribing; States with PDMPs and especially those with proactive PDMPs have lower rates of treatment admissions, reduced doctor shopping, and diversion; States with PDMPs have smaller increases in opiate exposures related to abuse and misuse, and lower outpatient drug claims; PDMPs can reduce the need for law enforcement and help monitor compliance and abstinence; and PDMP data can assist in substance abuse treatment and medical examiner practice. Brief descriptions of research studies, evaluations, surveys, and other reports that have demonstrated the effectiveness of PDMPs are included in this report. 57 endnotes