Independently, our two groups collaborating in this report performed association studies to consider the influence of the TNF region within the human MHC on the presence of colorectal cancer. In the Glasgow Study, 84 colorectal cancer patients were compared with 91 controls at the TNFa microsatellite locus. Analysis of individual alleles by Fisher's exact test revealed a significant overrepresentation of the TNFa2 allele in the colorectal cancer group, after correcting for multiple comparisons. In the Essen Study, 47 colorectal cancer patients were compared with 117 matched controls, and the hypothesis of TNFa2 overrepresentation in colorectal cancer was confirmed. These data provide evidence for the involvement of the TNF locus in the pathogenetic etiology of colorectal cancer.