Administrative data show that among surgical patients, readmission rates are highest in vascular surgery. Herein we analyze the contribution of planned readmissions and patient comorbidities to high readmission rates in vascular surgery.The 2012 to 2014 American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) data set was analyzed for overall and unplanned readmissions. Bivariable and multivariable risk adjustment analyses were performed using patient comorbidities to compare risks of overall and unplanned readmissions in vascular surgery compared with other specialties.Among 1,164,421 surgical patients, 86,403 underwent a vascular operation (other specialties included general surgery, 587,829 [51%]; orthopedic surgery, 211,507 [18%]; gynecology, 82,771 [7%]; urology, 62,153 [5%]; neurosurgery, 55,030 [4.7%]; plastic surgery, 32,318 [3%]; otolaryngology, 31,070 [2.6%]; and thoracic surgery, 15,340 [1%]). Incidence of 30-day readmission was 10.2% for vascular and 5.5% for other specialties (P < .0001). Planned readmissions were more frequent for vascular than for other specialties (8.8% vs 5.4%; P < .0001). In unadjusted analysis, vascular patients had significantly greater risk for overall readmission (odds ratio [OR], 1.97; 95% confidence interval [CI], 1.93-2.02; P < .0001) and unplanned readmission (OR, 1.89; 95% CI, 1.84-1.93; P < .0001) compared with other specialties. In bivariable analysis, vascular patients were older (67 ± 13 vs 56 ± 17 years) and had more comorbidities such as diabetes (31% vs 14%), dialysis dependence (6.3% vs 0.9%), American Society of Anesthesiology class III/IV status (84% vs 41%), and many others (all P < .0001). After risk adjustment for baseline differences between groups, vascular patients had a marginally greater overall risk of readmission compared with other specialties (OR, 1.04; 95% CI, 1.01-1.07; P < .0001), but the risk of unplanned readmission was not significantly different (OR, 0.98; 95% CI, 0.95-1.01; P = .13).Incidence of 30-day readmission after vascular surgery appears high, but after account for planned readmissions and risk adjustment, the risk of unplanned readmission is similar to that in other surgical patients. Thus, the use of readmission rate as a quality measure must account for more frequent planned vascular readmissions and patient-specific differences between vascular surgery and other specialties.