L-CAM is a cell adhesion molecule which is expressed at the intercellular borders of most epithelial cells. L-CAM has been demonstrated to act as an invasion suppressor in carcinoma cell lines. In order to determine whether or not L-CAM expression might distinguish between invasive and non-invasive or metastatic and non-metastatic colon neoplasms, we studied L-CAM expression in normal colon mucosa, colon adenomas with various degrees of dysplasia, and colon carcinomas by immunohistochemistry, using the 6F9 monoclonal anti-L-CAM antibody. Normal mucosa showed evenly distributed distinct L-CAM immunoreactivity along intercellular borders. In adenomas and carcinomas, a similar though weaker expression was observed. This pattern showed a tendency to decrease in parallel with decreasing differentiation. However, no correlation was found with Dukes stage or area within the tumour. In some carcinomas, L-CAM was expressed at the luminal surface of the cells. In others, L-CAM expression was not found. These results suggest that L-CAM expression is disregulated or lost as an early event in the development of colon neoplasia and indicate that L-CAM expression does not correlate with invasive or metastatic potential.