[en] Colorectal cancer (CRC) is the second leading cause of cancer-related death in the Western world. In Egypt; there is an increasing incidence of the disease, especially among patients ≤40 years age. While CRC have been reported in low incidence rate in developing countries, it is the third most common tumor in male and the fifth common tumor in females in Egypt. Early diagnosis and surgical interference guarantee long survival of most CRC patients. Early diagnosis is impeded by the disease onset at young age and imprecise symptoms at the initial stages of the disease. As in most solid tumors, the malignant transformation of colonic epithelial cells is to arise through a multistep process during which they acquire genetic changes involving the activation of proto-oncogenes and the loss of tumor suppressor genes. Recently, a candidate tumor suppressor gene, KLF6, which is mapped to chromosome 10p, was found to be frequently mutated in a number of cancers. There are some evidences suggesting that the disruption of the functional activity of KLF6 gene products may be one of the early events in tumor genesis of the colon. The main objective of the present study was to detect mutational changes of KLF6 tumor suppressor gene and to study the loss of heterozygosity (LOH) markers at chromosome 10p15 (KLF6 locus) in colorectal lesions and colorectal cancer in Egyptian patients. The patients included in this study were 83 presented with different indications for colonoscopic examination. Selecting patients with colorectal pre-cancerous lesions or colorectal cancer was done according to the results of tissue biopsy from lesion and adjacent normal. The patients were classified into three main groups; (G I) Cancerous group, (G II) polyps group including patients with adenomatous polyps (AP), familial adenomatous polyps (FAP) and hyperplastic polyps (HP) and (G III) Inflammatory Bowel Diseases (IBD) including patients with ulcerative colitis (UC) and Crohn's disease (CD). Purified DNAs which were extracted from the tissue samples, PCR amplified and subjected to the following examinations: 1- Detection of KLF6 mutations by using SSCP-silver staining technique and DNA sequencing by using BigDye Terminator v3.1 Cycle Sequencing kit using Biosystem automated sequencer (The ABI PRISM 3100 Genetic Analyzer). 2- Determination of Loss of heterozygosity (LOH) on chromosome 10 p15 regions (KLF6-locus) by using three micro satellite markers which includes KLFM1, KLFM2, and KLFM4. Data from the present study could be summarized as follows: In G I, 55.3% of cases had abnormalities in KLF6 gene (mutations and LOH). LOH was detected in 29% of investigated samples while KLF6 mutations were detected in 44% of cases. In G II, 57% of cases had abnormalities in KLF6 gene (mutations and LOH). LOH was detected in 55% of investigated samples while mutations of KLF6 gene were detected in 26% of investigated samples. In G III, 50% of samples had abnormalities in KLF6 gene (mutations and LOH). LOH was detected in 36.4% of investigated samples while mutations of KLF6 gene were detected in 27.3% of investigated samples. Most of the mutations reported were of the missence and /or Trans version type and were almost in exon 2. In conclusion, our data highlight for the first time a role of KLF6 gene in the progression of Egyptian colorectal carcinogenesis where the results suggest that KLF6 gene alteration is involved in the progression of Egyptian colorectal carcinogenesis from both sporadic adenomatous polyps and ulcerative colitis pathways. Detecting mutational sites differing from that detected in western populations may be a characteristic of Egyptian CRC due to environmental and genetic factors. The detections of such genetic abnormalities may also be used as a marker for the early uncovering of colon cancer cases. It is recommended that those who have pre-neoplastic colon lesions in which the KLF6 gene has mutated or lost its heterozygosity should experience more frequent colonoscopic examinations for the detection of doubtful malignant changes. The pres ent study also paves the way to further research needed to elucidate the possible role of KLF6 protein in the trans activation of other genes involved in cell cycle regulations and apoptosis. It also supports the possibility of using KLF6 gene as a target for gene therapy in colorectal cancer.