OBJECTIVES: To study the impact of post-operative ileus (POI) on health care utilization and costs in colectomy surgery patients in the United States. METHODS: A retrospective cohort study design was used. Adult patients with a principal procedure code for colectomy (ICD-9 codes 45.71 – 45.79), discharged between Jan. 2004 and Dec. 2004 were identified from Premier's Perspective Comparative Database, an inpatient records database from over 500 hospitals in the United States. The colectomy patients were further classified for the presence of POI, defined as presence of paralytic ileus (ICD-9 code 560.1) and/or digestive system complications (ICD-9 code 994.1) during the study period. Hospital length of stay (LOS), ICU LOS, ventilator usage, and hospitalization costs were compared using t-tests and chi-square tests as appropriate. RESULTS: A total of 17,896 patients with primary procedure code for colectomy were identified, of which 3,115 (17.4%) patients were classified for presence of POI, including paralytic ileus (N= 2,732; 15.3%) and digestive system complications (N=1,899; 10.6 %), with significant overlap between the two (N= 1516; 8.5%). A majority of the patients with POI were male (54.9%), caucasian (70.9%) and in the 51-64 year age group (51%). The average hospital LOS was significantly higher (p<0.001) in patients with POI (13.6 ± 13.3 days) compared with patients without POI (8.6± 9.5 days). The average ICU LOS was significantly higher (p<0.001) in patients with POI (2.4 ± 8.6 days) compared with patients without (1.2± 9.5 days). Ventilator usage was found to be significantly higher (p<0.001) in the POI group (17.0%) compared to those without (12.4%). Average hospitalization costs were significantly higher (p<0.001) in the patients with POI ($25,089± 35,386) than those without POI ($16,907 ± 29,320). CONCLUSION: Post-operative ileus in colectomy patients is associated with increased hospital resource utilization. Prevention of POI could reduce hospital length of stay and costs.