Colorectal cancer (CRC) is the most common cancer type and has high mortality rate at the third in the World and Vietnam. Currently, the number of patients with colorectal cancer tends to increase. The targeted therapy that uses EGFR (epidermal growth factor receptor) inhibitors is becoming an indispensable part of the process of controlling the progression of the disease. However, the KRAS mutations are major cause of resistance to EGFR inhibitor in treatment to colorectal cancer. In this study, the mutations in exon 2, 3, 4 in KRAS gene of patients with colorectal cancer were determined by direct sequencing from PCR products. The results showed that the authors did not found the mutations which were said to be affect to effect treatment as has been published. However, the authors determined six patients (KRIO, II, 12, 14, 15, 17) who have mutation point M67V
one patient (KR7) have mutation VlO3D and two patients (KR7, 9) have mutation MIIIK. The mutations at codon M67V and VI03D did change the spatial structure of KRAS protein in these positions. So, further analysis is needed to understand the associations between KRAS mutations and the influence of these mutations on effective treatment in patients with CRC.