The AHRQ Patient Safety Indicators (PSIs) represent quality measures that make use of a hospital's available administrative data. The PSIs reflect the quality of inpatient care but also focus on preventable complications and iatrogenic events. Investigators have found PSIs to be a useful tool for understanding adverse events and identifying possible areas of improvement within health care delivery systems. Although relying on administrative data has clear limitations, select PSIs have been shown to accurately identify certain accidental inpatient injuries. The AHRQ Web site offers publicly available comparative data, along with resources and tools. Patient safety measurement methods are discussed in an AHRQ WebM&M perspective.