Recent studies have demonstrated the cancer related role of genes that function in the repair of DNA damage. Inherited mutation of one of mismatch repair (MMR) genes results in hereditary non polyposis colorectal cancer (HNPCC). Even though HNPCC is the most common hereditary colon cancer, awareness of the disease among the public and health care providers is low and needs to be revived and established. The syndrome accounts for approximately 5% of all colorectal cancers and for about 50% of young cases. Five MMR genes have been implicated in HNPCC, but the majority of the mutations (95%) are found in MLH1 and MSH2 genes. One hundred young patients ( 61.2%).The mutation group compared to non mutation group had positive family history (Park criteria) (19% versus 1.4%), high prevalence of right sided tumors 51.6% versus 26%), high incidence of poorly differentiated tumors(61.3%), high mucinous tumors(45.2%), but less lymph nodal involvement. Synchronous polyps were significantly higher in mutation group (19.4%) and the only case with synchronous tumor was among the mutation group. In conclusion, the prevalence of mismatch repair gene in the studied young patients with CRCs is (31%), which is lower than the same age group of Western CRCs patients (45%).