Bevacizumab (Bev) plus chemotherapy is a standard first-line treatment in metastatic colorectal cancer (mCRC), however to date no predictive factors of response have been identified. Results of our previous analysis on patients enrolled in a randomized prospective phase III multicenter study (ITACa study) showed a predictive value of Vascular Endothelial Growth Factor (VEGF) polymorphism (VEGF + 936), a 27-nucleotide variable number tandem repeat (VNTR) of the endothelial nitric oxide synthase (eNOS) gene and eNOS + 894 polymorphism. mCRC patients, treated with Bev plus chemotherapy, were included in this prospective validation trial. eNOS + 894G > T was analyzed by Real time PCR, while the eNOS VNTR and VEGF + 936C > T were determined by standard PCR and direct sequencing analysis. These polymorphisms were assessed in relation to progression-free survival (PFS), overall survival (OS) and objective response rate (ORR). These three polymorphisms were not predictive of PFS (p 0.91, 0.59 and 0.09, respectively), and OS (p 0.95, 0.32 and 0.46, respectively). Moreover, the haplotype analyses did not confirm what was found in our previous study; patients bearing a specific haplotype of eNOS had not significantly improved outcomes. This prospective study failed to validate the predictive impact of eNOS and VEGF polymorphisms for response to Bev plus first-line chemotherapy in mCRC patients.