Abstract: Abstract In order to study the clinical changes of colorectal carcinomas, 612 Cases with colorectal carcinomas diagnosed with cndoscopy and confirmed pathologically from september 1977 to June 1994were assighed to youth groups and middleold aged to senior groups of three years, The result shows: (1)The ineidcnce of coloreetal carcinomas undergoes a trchd of clcvating. (2) The differenees between the two sexos on the age get less and less obvious. (3) Clinical presentations arc mainly up to the locations of the neoplasms rather than the ages of the patients. (4) While rectum remains the most common locus of coloreetal carcinomas, carcinomas in the right colon are not rare. (5) Colonal carcinomas of the left colon are found more in middle old aged to senior groups than in youth groups, while in the right colon except ceeum, the situation is just the opposite.