Background: Although single-site studies have reported reductions in coronary artery bypass graft (CABG) surgery length of stay (LOS) over the last 15 years, less information is available regarding overall temporal trends and interhospital variability. This study examined trends in postoperative LOS, associated rates of transfer at discharge and variation among hospitals in LOS at CABG hospitals in New York State. Methods: Trends in postoperative LOS and transfers at discharge for 105 842 CABG patients treated in 30 hospitals in New York between 1992 and 1998 were first described graphically. Mixed models were then used to assess temporal trends and interhospital variability in LOS, accounting for differences in patient risk and within-hospital correlation in outcomes. Clinical and LOS data were obtained from the Cardiac Surgery Reporting System. Additional information was extracted from the New York Statewide Planning and Research Cooperative System. Results: Postoperative LOS decreased 30% between 1992 and 1998 after adjusting for patient risk. A concurrent increase in the probability of nonacute patient transfers occurred over time, with the most pronounced increase in patients with stays exceeding 5 days. Underlying the downward trend in LOS was substantial interhospital variability that peaked in 1994 and remained significant in 1998. Stays were longer at hospitals located in New York City. Conclusions: The downward shift in LOS observed in the 1990s was achieved in part by an increase in nonacute care transfers, reflecting a shift in care setting. After decreasing trends in postoperative stays tapered off, significant variability among hospitals remained. © 2006 Mosby, Inc. All rights reserved.