Short, unnecessary hospitalizations are the largest contributor to erroneous Medicare payment. A team of medical, nursing, case management, and coding and billing professionals used process improvement techniques to reduce inappropriate 1-day admissions among 20 hospitals with high 1-day-stay utilization. Interventions included performance feedback, root cause analyses, process redesign, monthly progress monitoring, and quarterly pattern analyses. Over a 6-month period, the unweighted average admission error rate was reduced from 39% to 21% (p < .01). An estimated 1,396 1-day stays were prevented or denied payment, resulting in an annual savings of $6 million for Medicare's Hospital Insurance Trust Fund. [ABSTRACT FROM AUTHOR]