Confocal Raman microscopy system was used to investigate the etiologyof colorectal cancer at the molecular level. A total of two hundred and thirtyfour micro-Raman spectra were measured from thirty nine patients for surgicallyresected colorectal cancer specimens and adjacent normal tissues in the region900-2 100 cm-1. Two bands at 1 064 and 1 134 cm-1 which are attributed to theall-trans bond stretching vibrations of the C—C lipid skeleton decreased incolorectal cancer tissue samples. The ratio of the Raman band intensity at 1 299cm-1assigned to in-phase CH2 twisting vibrations of lipids to that at 1 264 cm-1from CH in-plane deformation was different for colorectal cancerous and normaltissues. The mean values of the (I1 299/I1 264) were 3.17 for normal tissues and1.33 for cancer tissues using the software function of “Compare Means”.Further, the scatter plots were used for grouping the ratio of Raman intensity at1 299 to 1 264 cm-1 according to tissue pathologic types by graph of theSPSS16.00 software. The decision lines (I1 299/I1 264=1.96) separates betweencancer and normal tissue with a coincidence rate of 94% (188/200) according tothe histological results by graph. The results show that the differences betweencancer and normal tissue spectra appear to arise from a decrease in the degree ofthe longitudinal order and an increase in the degree of unsaturation of lipid,which causes the fluidity of lipid to increases when normal cells are transformedinto cancerous cells.Cancer