Advocates of physician-owned single specialty hospitals (SSHs) maintain that, through healthy competition, SSHs pressure competitor hospitals in local markets to improve performance. This paper investigates data trends on the effects of SSH entry on a potential indicator of quality of care in general hospital competitors: nurse staffing levels. We examined registered nurse (RN) staffing from 1997 to 2004 in ten states in which there was considerable SSH entry during this period. Regression estimates used longitudinal panel data models with hospital fixed effects to compare changes in numbers of RNs in general hospitals located in markets with SSHs with general hospitals located in markets where there were no SSHs. Results indicate that hospitals located in markets with orthopedic/surgical SSH presence raised their RN nurse staffing levels. Whether or not these changes are associated with improved patient outcomes is unknown.