Background: Bevacizumab, a humanized antibody against the molecular target endotelial growth factor VEGF-A, has incorporated to the standard of care of metastatic colon-rectal cancer (mCRC). A recent study has suggested that the left colon localization of the primary tumor may be a factor associated with a poorer survival in individuals treated against mCRC with bevacizumab including chemotherapy. Our objective was to analyze the impact of the localization of the primary tumor on the survival of patients with mCRC treated with bevacizumab. Methods: Prospective cohort study conducted in a tertiary-care hospital in Spain. Twenty-nine consecutive patients with mCRC who started a first-line therapy including bevacizumab were included. Patients were followed up until death, lost to follow-up or the censoring date (31th August, 2013). The primary end-point of the study was death from any cause. Predictors of survival, including the localization of the primary tumor, were assessed. Results: The median (Q1-Q3) age was 59 (52-67) years and 13 (45%) patients were male. Chemotherapy scheme was XELOX in 13 (45%) patients, FOLFOX in 8 (28%), FOLFIRI in 5 (17%), XELIRI in 2 (7%) and capecitabine in 1 (3%) patient. The localization of the primary tumor were distributed as follows: rectum in 6 (21%), sigmoid colon in 9 (31%), left colon in 9 (31%) and right colon in 5 (17%) patients. After a median (Q1-Q3) follow-up of 29 (13-41) months, 19 (66%) patients died. There were no patients lost to the follow-up. The mean (SD) survival in patients with left colon cancer was 25 (8) months whereas it was 47 (7) months in the remaining population (p = 0.1). The low sample size precluded to perform reliable multivariate analyses. Conclusions: Our study suggests that left colon localization of the primary tumor may have a worse prognosis in patients with mCRC treated with bevacizumab. Although no statistically significant differences have been observed, this fact may have been a consequence of the limited power of the analysed sample. Collaborative studies should be perfomed in order to clarify this issue.