This AHRQ-funded study describes the association between dimensions of effective quality improvement (QI) and their impact on hospital-based patient safety indicators (PSI). Investigators combined data from a national survey of hospital QI practices with four PSIs in demonstrating that physician involvement in QI was the only significant association with improved indicator scores. Involvement of senior management and multiple hospital units in a QI effort failed to demonstrate a significant association with PSI values. This study expands on previous efforts at understanding the organizational factors involved in achieving patient safety improvement.