To investigate the growth and progression of colorectal cancer, cell production versus cell loss in colorectal cancer was examined using the proliferating cell nuclear antigen (PCNA) positivity rate and apoptotic index (AI). Cell loss was then examined using AI in the mucosa adjacent to colorectal cancer. The higher the PCNA positivity rate, the higher the apoptotic index in colorectal cancer. These results suggested that changes in cell production and cell loss may be closely correlated and play a role in the growth and progression of colorectal cancer. In patients with advanced colorectal cancer, the mucous composition of the adjacent mucosa was classified as sialomucin-predominant. Apoptosis at the proliferating zone in the mucosa adjacent to colorectal cancer (one or two glandular ducts) was also examined using the TUNEL method. This suggests that the mucosa adjacent to cancer is involved in apoptosis.