This study examined the relationship between nurse staffing and hospital characteristics and specific patient safety measures, such as nosocomial infection rates and incidence of decubitus ulcers. Lower nurse-to-patient ratios and increased overtime both negatively impacted patient safety and in-hospital mortality, but hospital characteristics were not associated with safety measures. The study confirms and extends the findings of previous studies, which have demonstrated that lower nurse staffing and extended shifts are associated with self-reported errors and increased mortality.