The expression of tetranectin in colonic neoplasia was evaluated by determining the tissue distribution by immunohistological analysis of tissue sections and the antigen levels in tissue homogenates and plasma. In normal colonic mucosa tetranectin staining was predominantly found in the goblet cells whereas in adenocarcinomas this staining was confined to the tumour stroma. Colonic adenomas, benign precursors of adenocarcinomas, showed fewer tetranectin positive goblet cells and in some cases showed tetranectin expression in the stroma. Within the tissue homogenates no differences were found in the tetranectin levels between normal mucosa, adenomas and carcinomas. Patients with colonic cancer were found to have significantly decreased plasma tetranectin levels compared to healthy controls. Thus, colonic neoplasia is associated with a change in the tissue distribution of tetranectin, without an obvious change in the tissue level, and a low plasma tetranectin level.