Colon polyps are small growths that arise in the large intestine. If present for several years they can grow in size and lead to the development of colon cancer and bleeding. Probably 90% of colon cancers arise from previously benign polyps.
Not all polyps are of the cancerous variety, but until they are analyzed in a lab, we cannot be certain as to the tissue type and that is why all polyps are removed.

Currently, there are several methods by which we screen people for colon cancer. These include colonoscopy, screening sigmoidoscopies with stool hemoccult testing barium enema.

Most organizations are suggesting screening begining at age 50. In fact almost all
insurance companies now reimburse for screening colonoscopies begining at age 50.
The appropriate interval after that is not clear yet, but it probably would be every five to seven years assuming that initial colonoscopy, which we call the 'index' colonoscopy, is normal. With a family history of colon cancer, the screening should begin at an early age and it depends upon the age of the colon cancer development in the parent, brother or sister.