L-CAM, also known as E-cadherin, is a cell adhesion molecule expressed on the plasma membranes of epithelial cells at the intercellular interface. From in vitro gene transfection experiments the idea has been conceived that loss of L-CAM expression might be related to the invasive capacity as well as metastatic potential of tumour cells. In several tumours a relation between the grade of differentiation and L-CAM expression has been noticed: loss of differentiation appears to be associated with loss of L-CAM immunoreactivity. Also, in lymph node metastases of poorly differentiated carcinomas loss of L-CAM expression was demonstrated. In this study we describe L-CAM expression in lymphogenous and haematogenous metastases of large bowel adenocarcinomas, using an indirect immunoperoxidase method with the monoclonal anti-L-CAM antibody 6F9. All the metastases studied--lymphogenous as well as haematogenous--demonstrated L-CAM immunoreactivity in a pattern comparable to that of primary tumours. Intratumour heterogeneity in expression was noted, with normal intercellular, apical (non-functional), and focally negative areas in the same tumour. The data indicate that primary tumours and their metastases do not differ strikingly in their pattern of L-CAM expression. This would be consistent with transient rather than constitutive down-regulation of L-CAM in invasive and metastatic cancer cells.