In colorectal cancer an association has been found between lack of epithelial basement membrane (EMB) immunostaining in the tumour centre and more extensive malignant spread. Interestingly, ultrastructural investigations suggest that EBM loss at the tumour periphery may be part of an invasive mechanism. To further assess the significance of EBM deficiencies in different tumour areas, we carried out a detailed study of the basement membrane laminin immunostaining patterns in 130 cases of colorectal carcinoma. We find that discontinuous EBM staining in the tumour centre is associated with poor tumour differentiation (p less than 0.005), presence of lymph-node metastases (p less than 0.02), and more advanced Dukes stage (p less than 0.02). The latter association is strengthened by excluding cases in which numerous polymorphonuclear leukocytes (PMNs) are present adjacent to EBM breaks, suggesting that these inflammatory cells are a confounding factor. Discontinuous EBM staining is more frequently observed in tumour deep to muscularis propria than in submucosal tumour (p less than 0.02), indicating intra-tumoral variation. At the tumour periphery, extensive EBM discontinuity shows no association with lymph-node involvement, but is linked with deeper local invasion (p less than 0.05). While EBM staining patterns around central and peripheral tumour glands are related (p less than 0.001), staining around peripheral glands is almost invariably more discontinuous. However, EBM lack at the tumour periphery is not as absolute as previously suggested, since in 18% of tumours fewer than 25% of peripheral tumour glands show EBM breaks. This appears consistent with the hypothesis that invasive changes at the tumour periphery are temporary and reversible.