D-Loop of mitochondrial DNA is non-coding regions including two hypervariable regions HVI and HVII. Most of the D-Loop sequence alterations are polymorphic but there are some somatic mutations linked to some diseases, particularly the neuromuscular diseases and cancers including colorectal cancers. This study aimed to identify some mitochondrial DNA sequence variations of D-Loop in a group of colorectal cancer patients in Vietnam and test the relationship between these variations and the disease. Using PCR-RFLP combining with DNA directly sequencing method in order to determine mutations of A 188G, G203A and G16390A, the authors detected 7 out of 98 (7.2 percent) colorectal cancer tissue samples with G16390A alteration in the HVI region of mitochndrial DNA and 2 out of 29 (6.9 percent) blood samples of control people with this alteration. A 188G and G203A alterations were not found !n the HVII region of mitochondrial DNA in colorectal cancer tissue samples. DNA sequencing results of samples containing G 16390A alteration and some other ones revealed different variations: T16304C, A16309G, T16519C, A73G, T146C, A263G... of mitochondrial DNA in colorectal cancer tissue samples. However, the rate of G16390A alteration is not significantly different between colorectal cancer and control groups (bloodl samples) (p0.05). G16390A alteration was not correlated with gender, age of patients, location (tumor tissues or adjacent tissues), site of tumor and TNM stage of colorectal cancer patients (p0.05).