In a report out today, they say colon cancer has fallen 30% over the past decade in people over age 50, and colonoscopies are getting much of the credit.
The rate of testing has risen from 19% in 2000 to 55% just 10 years later.
Death rates have also declined, at about 3% a year over the past decade.
Doctors recommend people with an average risk start getting screened at age 50.
Colonoscopies actually prevent cancer, because it allows doctors to detect and remove polyps before they turn malignant.