OBJECTIVES: Preoperative determination of the grade of dysplasia in intraductal papillary mucinous neoplasms (IPMNs) is necessary for optimal management. Previous data have suggested that serum neutrophil-to-lymphocyte ratio (NLR) can predict invasive disease in patients with IPMN. METHODS: A prospectively maintained database was queried for consecutive patients who underwent resection of IPMN. Exclusion criteria included recent diagnosis of cancer, immunosuppression, and infection or jaundice within 1 month of operation. A complete blood count with differential within 30 days of operation was used to calculate NLR. RESULTS: Within the study period, 446 patients underwent resection for IPMN, and 348 patients (78%) met the inclusion criteria. Low-grade dysplasia was present in 60 patients (17%), 137 patients (39%) had intermediate-grade dysplasia, 76 (22%) had high-grade dysplasia, and 75 (22%) had invasive carcinoma. A higher NLR was associated with invasive carcinoma as compared with noninvasive disease (3.00 vs 2.68, P = 0.039). There was no difference in NLR between patients with high-risk (invasive and high-grade) and low-risk (low-grade and intermediate-grade) lesions (2.80 vs 2.71, P > 0.95). CONCLUSIONS: Neutrophil-to-lymphocyte ratio was significantly higher in patients with IPMN-associated invasive carcinoma as compared with patients with noninvasive disease; however, NLR was not helpful in differentiating between high- and low-grade lesions.