An estimated 175,000 people have Lynch syndrome in the UK, however 95% of those do not know they have it. NICE recommends that microsatellite instability (MSI) testing or immunohistochemistry (IHC) should be used on all colorectal cancers, when first diagnosed, to detect abnormalities that might mean the presence of Lynch Syndrome. Where these tests show the person has a risk of having Lynch syndrome, the guidance recommends that further tests are carried out to confirm the diagnosis. Because Lynch Syndrome is an inherited condition, a positive test can also lead to testing for family members. While these tests have been available for a while, there is currently wide variation in the provision of testing for Lynch syndrome and other inherited colorectal cancers. Expanding testing to all people with colorectal cancer will increase the detection of Lynch syndrome and identify families who could benefit from genetic testing to determine if other family members have the condition. This could lead to increased surveillance and consequently improved patient outcomes through earlier diagnosis and treatment.