This study reports on findings from a comprehensive study of 168 hospitals and clarifies the impact of nurse staffing levels on patient outcomes and factors that influence nurse retention. Specifically, we examined whether risk-adjusted surgical mortality and rates of failure-to-rescue (deaths in surgical patients who develop serious complications) are lower in hospitals where nurses carry smaller patient loads. In addition, we ascertained the extent to which more favorable patient-to-nurse ratios are associated with lower burnout and higher job satisfaction among registered nurses. We also estimated excess surgical deaths associated with the different nurse staffing ratios vigorously debated in California. Finally, we estimated the impact of nurse staffing levels proposed in California on nurse burnout and dissatisfaction, 2 precursors of turnover. Our findings offer insights into how more generous registered nurse staffing might affect patient outcomes and inform current debates in many states regarding the merits of legislative actions to influence staffing levels.