The size of the regional lymph nodes, germinal center, and paracortical areas, and the degree of perivascular lymphocyte cuffing (PLC) at the edges of 519 carcinomas of the large bowel have been analyzed microscopically and assessed quantitatively. Hyperplasia of these lymphoid areas, defined as relative or absolute size exceeding the median for the tumor stage, has been related to cancer-specific survival data for each of Dukes' Stages A, B, and C, and for disseminated disease commonly referred to as Stage D. Germinal center hyperplasia was associated with a major survival advantage in Stage B (P = 0.003) and in Stage C (P = 0.04) if present in tumor-involved lymph nodes. Paracortical hyperplasia related favorably to survival in Stages B and C; in Stage C such hyperplasia was most favorable if present in tumor-involved lymph nodes (P = 0.009). PLC related to favorable survival data only in Stage B. Lymphoid hyperplasia showed no correlation with survival in Stages A and D.