There is widespread debate over hospital nurse staffing: what is the correct nurse-to-patient ratio, and how best can hospitals recruit and retain nurses? Linda H. Aiken, PhD, RN, discusses a recent study and her own work as she explores this question. A study examining the nurse-to-patient ratio in intensive care units (ICU) in Maryland hospitals by Pronovost et al (Effective Clinical Practice. 2001;4: 1999-206), found that patients in hospitals where ICU nurses care for three or more patients have significantly increased risk for medical complications compared with patients in hospitals where ICU nurses care for one or two patients. Pronovost et al's research also suggests that fewer nurses could cost more: inadequate nurse staffing levels can lead to longer lengths of stay. Aiken's twenty-hospital study of AIDS patients found that the hospitals that had the most favorable nurse-to-patient ratios had significantly shorter overall length of stay as well as fewer ICU days. Aiken also argues that the effects of excellent nurse staffing can be undermined in organizations that restrict nurses' autonomy to act within their scope of expertise, that provide inadequate administrative support, or that fail to give nurses authority commensurate with their high level of responsibility for patient well-being. Increasing evidence suggests that more nurses lead to better patient outcomes, and the key to recruiting and retaining adequate numbers of nurses is to substantially improve working conditions in U.S. hospitals.