BACKGROUND Risk factors for perioperative mortality after coronary artery bypass graft (CABG) surgery have been extensively studied. However, which factors are associated with early readmissions following CABG surgery are less clear. OBJECTIVE To identify significant predictors of readmission within 30 days following CABG surgery. METHODS Causes for readmission within 30 days were investigated for all patients discharged after CABG surgery in the state of New York from January 1, 1999, through December 31, 1999. A variety of patient demographics, preoperative risk factors, complications, operative and postoperative factors, and provider characteristics were considered as potential predictors of readmissions. METHODS Hospital readmissions within 30 days of discharge following CABG surgery. RESULTS Of 16 325 total patients, 2111 (12.9%) were readmitted within 30 days for reasons related to CABG surgery. The most common causes of readmission were postsurgical infection (n = 598 [28%]) and heart failure (n = 331 [16%]). Eleven risk factors were found to be independently associated with higher readmission rates: older age, female sex, African American race, greater body surface area, previous myocardial infarction within 1 week, and 6 comorbidities. After controlling for these preoperative patient-level risk factors, 2 provider characteristics (annual surgeon CABG volume <100, hospital risk-adjusted mortality rate in the highest decile) and 2 postoperative factors (discharge to nursing home or rehabilitation/acute care facility, length of stay during index CABG admission of > or =5 days) were also related to higher readmission rates. CONCLUSIONS Readmission within 30 days following discharge is an important adverse outcome of CABG surgery. Continued attempts should be made to explore the potential of readmission as a supplement to mortality in assessing provider quality.