RAS and BRAF mutation and primary tumour sideness are prognostic and predictive factors in metastatic colorectal cancer (mCRC). We aimed to investigate RAS-BRAF mutation rates and responses to biologic agents the effects of tumour sideness on survival. This was a retrospective study conducted at three Turkish institutes. 303 patients with mCRC who were examined for tumour RAS and 172 examined for tumour BRAF mutations between 2006-2018. A total of 303 (M/F= 186/117) patients were included to study. Median age was 63 (range: 23-86) years. Median follow-up was 22.8 (range: 19.1-26.4) months. In the RAS wild type population; ad-dition to anti-EGFR agents to standard chemotherapy (CT) had better outcomes than Bevacizumab+CT. Median PFS was improved with anti-EGFR agents (Respectively PFS; 14.5 months, 8.7 months) (log rank p= 0.007 HR= 0.59). Median OS was similar between CT+anti-EGFR and CT+Bevacizumab arms (Respectively OS; 29.3 months, 21.7 months) (log rank p= 0.418; HR= 0.75). RAS muta-tion rates were similar between right colon cancer (RCC) and left colon cancer (LCC), BRAF mutation rates were significantly increased in RCC (22.2 vs 2.7%, p< 0.0001). RCC (24.1%) had worse prognosis than LCC (75.9%). However, this difference was not significant (PFS: 10.4 vs 10.0 months (log rank p= 0.136) , OS: 21.5 vs 23.1 months (log rank p= 0.436). We concluded that in the patients with RAS wild type tumours, CT and anti-EGFR combination was reasonable approach for first line treatment. BRAF mutation, irrespective of CT regimen, was associated with poor survival and more common in RCC patients.