BACKGROUND: One major intent of the medical malpractice system in the United States is to deter negligent care and to create incentives for delivering high-quality health care. A study was conducted to assess whether state-level measures of malpractice risk were associated with hospital quality and patient safety. METHODS: In an observational study of short-term, acute-care general hospitals in the United States that publicly reported in the Centers for Medicaid & Medicare Services Hospital Compare in 2011, hierarchical regression models were used to estimate associations between state-specific malpractice environment measures (rates of paid claims, average Medicare Malpractice Geographic Practice Cost Index [MGPCI], absence of tort reform laws, and a composite measure) and measures of hospital quality (processes of care, imaging utilization, 30-day mortality and readmission, Agency for Healthcare Research and Quality Patient Safety Indicators, and patient experience from the Hospital Consumer Assessment of Healthcare Providers and Systems [HCAHPS]). RESULTS: No consistent association between malpractice environment and hospital process-of-care measures was found. Hospitals in areas with a higher MGPCI were associated with lower adjusted odds of magnetic resonance imaging overutilization for lower back pain but greater adjusted odds of overutilization of cardiac stress testing and brain/sinus computed tomography (CT) scans. The MGPCI was negatively associated with 30-day mortality measures but positively associated with 30-day readmission measures. Measures of malpractice risk were also negatively associated with HCAHPS measures of patient experience. CONCLUSIONS: Overall, little evidence was found that greater malpractice risk improves adherence to recommended clinical standards of care, but some evidence was found that malpractice risk may encourage defensive medicine.