The adenomatous polyposis coli (APC) gene, mapped to chromosome 5q21 (Kinzler et al, 1991), plays a prominent role in the development of colorectal cancer, both in the autosomal dominant inherited familial APC syndrome (Bodmer et al, 1987; Groden et al, 1991; Joslyn et al, 1991; Kinzler et al, 1991; Nishisho et al, 1991) and in sporadic colorectal cancer (Fearon and Vogelstein, 1990; Miyoshi et al, 1992; Powell et al, 1992). Here, APC is linked to colorectal cancer.