OBJECTIVES: The aims of this study were to assess computed tomography enhancement of pancreatic neuroendocrine tumors (NETs), determine correlation with histological vascularity and fibrosis, and identify a biomarker for tumor aggression. METHODS: The arterial and venous enhancement of NET was calculated on computed tomography for 56 patients. Tumor size and vascularity/fibrosis were assessed. Tumor aggression was grouped by World Health Organization and Hochwald grade and the presence of metastases. Variables were assessed for correlation. Groups were compared using t test/Wilcoxon rank sum test. RESULTS: Arterial enhancement and dynamic washout (r = 0.35, P = 0.02; r = 0.34, P = 0.02, respectively) correlate with vascularity. There is inverse correlation between vascularity and fibrosis (r = −0.62, P < 0.001), but no correlation between enhancement and fibrosis. Metastatic NET had less arterial (mean, −2 [standard deviationi {SD}, 27.1] Hounsfield unit [HU]; 35.7 [SD, 57.5] HU; P = 0.01) and venous (12.6 [SD, 14.4] HU; 29.2 [SD, 38.3] HU; P = 0.04) enhancement and less washout (8.5 [SD, 18.5] HU; 26.8 [SD, 30] HU, P = 0.02) compared with nonmetastatic NET. These differences were not present when comparing by tumor grade. Arterial hypoenhancement was the only significant predictor of metastases. CONCLUSIONS: Aggressive tumors, as determined by metastases, but not histological grade, enhance less than nonmetastatic tumors.