Forty-three gastric cancers, 38 colon cancers, and 26 cancers of the rectum were diagnosed among indigenous Greenlanders in the 20-year period 1955--1974. When cases based on clinical evidence only were excluded, a comparison with Danes showed significant deficits for male gastric cancers for 1960--1964 and female rectal cancers for 1970--1974. For the 20 years as a whole, gastric cancers in females were significantly lower than expected. Eleven clinical gastric cancers, 5 clinical colon cancers, and an additional 34 malignancies suspected of being primary gastrointestinal cancers had not been exhaustively investigated, mainly owing to metastatic spread and old age at the time of diagnosis. It seems reasonable to assume that the incidences of gastric cancer and of colorectal cancer in Greenland did not differ greatly from the incidences in Denmark during the study period in spite of dietary differences. A more regular use of rather simple examinations in the diagnostic routine is necessary for future epidemiological studies.