APC*E1317Q is a low-penetrance variant of the APC gene suggested as a risk for the development of colorectal adenomas and carcinomas. There is very little in the literature describing the molecular details of APC*E1317Q in tumor tissue. We provide information about the molecular genetics of 3 patients with APC*E1317Q. For 1 patient, we show linkage to a specific APC allele. We further show that loss of heterozygosity of the APC gene in tumors from carriers of the APC*E1317Q mutation may involve the mutated allele, not just the wild-type allele, suggesting the APC*E1317Q missense mutation may not be pathologically significant in the development of colorectal tumors.