IMPORTANCE Hospital readmission rates following surgery are increasingly being used as a marker of quality of care and are used in pay-for-performance metrics. To our knowledge, comprehensive data on readmissions to the initial hospital or a different hospital after emergency general surgery (EGS) procedures do not exist. OBJECTIVE To define readmission rates and identify risk factors for readmission after common EGS procedures. DESIGN, SETTING, AND PARTICIPANTS Patients undergoing EGS, as defined by the American Association for the Surgery of Trauma, were identified in the California State Inpatient Database (2007-2011) on January 15, 2015. Patients were 18 years and older.We identified the 5 most commonly performed EGS procedures in each of 11 EGS diagnosis groups. Patient demographics (sex, age, race/ethnicity, and insurance type) as well as Charlson Comorbidity Index score, length of stay, complications, and discharge disposition were collected. Factors associated with readmission were determined using multivariate logistic regression models analysis. MAIN OUTCOMES AND MEASURES Thirty-day hospital readmission. RESULTS Among 177 511 patients meeting inclusion criteria, 57.1%were white, 48.8% were privately insured, and most were 45 years and older (51.3%). Laparoscopic appendectomy (35.2%) and laparoscopic cholecystectomy (19.3%) were the most common procedures. The overall 30-day readmission rate was 5.91%. Readmission rates ranged from 4.1% (upper gastrointestinal) to 16.8%(cardiothoracic). Of readmitted patients, 16.8%were readmitted at a different hospital. Predictors of readmission included Charlson Comorbidity Index score of 2 or greater (adjusted odds ratio: 2.26 [95%CI, 2.14-2.39]), leaving against medical advice (adjusted odds ratio: 2.24 [95%CI, 1.89-2.66]), and public insurance (adusted odds ratio: 1.55 [95%CI, 1.47-1.64]). The most common reasons for readmission were surgical site infections (16.9%), gastrointestinal complications (11.3%), and pulmonary complications (3.6%). CONCLUSIONS AND RELEVANCE Readmission after EGS procedures is common and varies widely depending on patient factors and diagnosis categories. One in 5 readmitted patients will go to a different hospital, causing fragmentation of care and potentially obscuring the utility of readmission as a qualitymetric. Assisting socially vulnerable patients and reducing postoperative complications, including infections, are targets to reduce readmissions.