Background: Diabetes is a known, but poorly understood sequela of pancreatic resection in a subset of patients. Our aim was to define the incidence and risk factors of postresection diabetes (PRD) after distal pancreatectomy (DP). Methods: A retrospective review of all consecutive patients undergoing DP at our institution from January 2004 through July 2010. Data was obtained from medical records, pathology reports, and postoperative imaging. Postoperative CT scans were evaluated to determine extent of resection, defined by site of transection as limited (adrenal or left), standard (superior mesenteric artery or left to adrenal), extended (neck), subtotal (into head). Comparisons between patients with and without PRD were evaluated using chi-square, Fisher's exact, and Wilcoxon rank sum tests. Univariate and multivariable associations with PRD were evaluated using logistic regression models and summarized with odds ratios and 95% confidence intervals. Results: Of 583 patients undergoing DP, 90 patients with pre-existing type I (n=24) or type II (n=66) diabetes were excluded. The remaining 493 patients represent the study population with a mean age of 57 years and BMI (kg/m2) of 27.4. Operative indications included benign lesions in 253 patients (51%) and malignancy in 240 (49%). Extent of pancreatic resection was limited in 141 patients (37%), standard in 87 (23%), extended in 128 (33%), and subtotal in 30 (8%). Postoperatively, 179 patients (36%) required no postoperative treatment, 269 (55%) required perioperative hyperglycemic control, and 45 (9%) developed diabetes including 34 requiring insulin, and 11 oral hypoglycemic medication. Patients developing PRD had higher mean preoperative glucose levels (98.2 vs. 112.1, p<0.001), BMI (27.3 vs. 29.1 kg/m2, p=0.019), estimated blood loss (594 vs. 845 ml, p=0.001), longer operative time (238 vs. 269 min, p=0.003), and greater pancreatic specimen length (9.3 vs. 10.9 cm, p=0.024). Incidence of PRD correlated with CT extent of pancreatic resection, occurring after limited resection in 4.2%, standard in 4.6%, extended in 13.2%, and subtotal in 30%. On multivariate analysis, factors associated with increased risk of PRD included preoperative glucose ≥126 (OR 10.06,p<0.001), BMI 5 unit increase (OR 1.6,p=0.011), extended (OR 3.37,p=0.031) or subtotal resection (OR 9.86,p<0.001), and blood transfusion (OR 2.38,p+0.037). Conclusion: Postresection diabetes occurs in approximately 9% of patients after DP. Factors associated with increased risk include elevated preoperative glucose, BMI, extent of resection, and need for blood transfusion. Three of these factors are easily attained preoperatively by clinical evaluation and expected pancreatic remnant based on CT imaging. These findings will help counsel patients pre and postoperatively about the risks of postresection diabetes after DP.