One of the questions that colorectal cancer patients and their families are very concerned about is whether colorectal cancer is contagious or not. Is it hereditary? Especially some parents who have children at home are very worried about transmitting or inheriting the disease to their children. In fact, colorectal cancer is a disease related to genetic mutation, so it is certainly not contagious. Therefore, even if an elderly person suffers from colorectal cancer, there is no need to isolate himself from his family, and he can still eat with his children and grandchildren and live together. In addition, colorectal cancer itself is not a hereditary disease, but it has a certain degree of heritability. That is to say, if an elderly person in the family suffers from colon cancer, it does not mean that the children will definitely get cancer as well, but they are more likely to get cancer than other people under the same living environment. Studies have shown that if a person with colorectal cancer is found in a particular family, then relatives related to him (parents, children, siblings) are significantly more likely to develop colorectal cancer, and the incidence of colorectal cancer is about 2-3 times higher than that of the general population. The risk of colorectal cancer is higher if two or more close relatives (parents or siblings) in the family have colorectal cancer. Especially for a young colorectal cancer patient, it is more closely correlated with genetic factors and the incidence of colorectal cancer is higher in his immediate family. Therefore, relatives of colorectal cancer patients should have colonoscopy as early as possible to detect colorectal cancer and treat it as early as possible. However, colorectal cancer is not particularly hereditary. In other words, unlike some hereditary diseases, if parents have the disease, their children will definitely develop it. Even if two people have exactly the same genetic background, if they are exposed to different environments, their probability of developing colorectal cancer is not the same. Therefore, children of colorectal cancer patients are not 100% likely to get colorectal cancer. Most colorectal cancers are sporadic, however, about 10%-15% of colorectal cancers have genetic background, among which familial adenomatous polyposis (FAP) accounts for 1-2%, hereditary non-polyposis colorectal cancer (HNPCC) accounts for 2%-7%, and others include dark spot polyposis (PJS) and juvenile polyposis. For this group of people it is important to have colonoscopy as early as possible and to review it regularly for early development and timely treatment.